diff --git a/.appveyor.yml b/.appveyor.yml
index bdad5f319..8c7527499 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -10,12 +10,12 @@ image:
 
 environment:
   libyaml_repo_url: https://github.com/yaml/libyaml.git
-  libyaml_refspec: release/0.2.2
+  libyaml_refspec: 0.2.2
+  PYYAML_TEST_GROUP: all
+
 #  matrix:
 #    - PYTHON_VER: Python27
 #    - PYTHON_VER: Python27-x64
-#    - PYTHON_VER: Python34
-#    - PYTHON_VER: Python34-x64
 #    - PYTHON_VER: Python35
 #    - PYTHON_VER: Python35-x64
 #    - PYTHON_VER: Python36
diff --git a/.travis.yml b/.travis.yml
index 3dfe3ad9c..b3185f959 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,25 +2,28 @@
 
 language: python
 
-sudo: false
-
 cache: pip
 
+env:
+  global:
+    - PYYAML_TEST_GROUP=all
+
 matrix:
   include:
     - python: 2.7
       env: TOXENV=py27
-    - python: 3.4
-      env: TOXENV=py34
     - python: 3.5
       env: TOXENV=py35
     - python: 3.6
       env: TOXENV=py36
-    - python: 3.7-dev
+    - python: 3.7
       env: TOXENV=py37
-    # This is broken on travis as of 2019/03/12
-    # - python: pypy
-    # env: TOXENV=pypy
+    - python: 3.8
+      env: TOXENV=py38
+    - python: 3.8-dev
+      env: TOXENV=py38
+    - python: pypy
+      env: TOXENV=pypy
 
 # build libyaml
 before_script:
diff --git a/CHANGES b/CHANGES
index 91f0255bb..e74edc224 100644
--- a/CHANGES
+++ b/CHANGES
@@ -4,6 +4,49 @@ For a complete changelog, see:
 * https://github.com/yaml/pyyaml/commits/
 * https://bitbucket.org/xi/pyyaml/commits/
 
+5.3 (2020-01-06)
+
+* https://github.com/yaml/pyyaml/pull/290 -- Use `is` instead of equality for comparing with `None`
+* https://github.com/yaml/pyyaml/pull/270 -- fix typos and stylistic nit
+* https://github.com/yaml/pyyaml/pull/309 -- Fix up small typo
+* https://github.com/yaml/pyyaml/pull/161 -- Fix handling of __slots__
+* https://github.com/yaml/pyyaml/pull/358 -- Allow calling add_multi_constructor with None
+* https://github.com/yaml/pyyaml/pull/285 -- Add use of safe_load() function in README
+* https://github.com/yaml/pyyaml/pull/351 -- Fix reader for Unicode code points over 0xFFFF
+* https://github.com/yaml/pyyaml/pull/360 -- Enable certain unicode tests when maxunicode not > 0xffff
+* https://github.com/yaml/pyyaml/pull/359 -- Use full_load in yaml-highlight example
+* https://github.com/yaml/pyyaml/pull/244 -- Document that PyYAML is implemented with Cython
+* https://github.com/yaml/pyyaml/pull/329 -- Fix for Python 3.10
+* https://github.com/yaml/pyyaml/pull/310 -- increase size of index, line, and column fields
+* https://github.com/yaml/pyyaml/pull/260 -- remove some unused imports
+* https://github.com/yaml/pyyaml/pull/163 -- Create timezone-aware datetimes when parsed as such
+* https://github.com/yaml/pyyaml/pull/363 -- Add tests for timezone
+
+5.2 (2019-12-02)
+------------------
+
+* Repair incompatibilities introduced with 5.1. The default Loader was changed,
+  but several methods like add_constructor still used the old default
+  https://github.com/yaml/pyyaml/pull/279 -- A more flexible fix for custom tag constructors
+  https://github.com/yaml/pyyaml/pull/287 -- Change default loader for yaml.add_constructor
+  https://github.com/yaml/pyyaml/pull/305 -- Change default loader for add_implicit_resolver, add_path_resolver
+* Make FullLoader safer by removing python/object/apply from the default FullLoader
+  https://github.com/yaml/pyyaml/pull/347 -- Move constructor for object/apply to UnsafeConstructor
+* Fix bug introduced in 5.1 where quoting went wrong on systems with sys.maxunicode <= 0xffff
+  https://github.com/yaml/pyyaml/pull/276 -- Fix logic for quoting special characters
+* Other PRs:
+  https://github.com/yaml/pyyaml/pull/280 -- Update CHANGES for 5.1
+
+5.1.2 (2019-07-30)
+------------------
+
+* Re-release of 5.1 with regenerated Cython sources to build properly for Python 3.8b2+
+
+5.1.1 (2019-06-05)
+------------------
+
+* Re-release of 5.1 with regenerated Cython sources to build properly for Python 3.8b1
+
 5.1 (2019-03-13)
 ----------------
 
@@ -17,7 +60,6 @@ For a complete changelog, see:
 * https://github.com/yaml/pyyaml/pull/61 -- Use Travis CI built in pip cache support
 * https://github.com/yaml/pyyaml/pull/62 -- Remove tox workaround for Travis CI
 * https://github.com/yaml/pyyaml/pull/63 -- Adding support to Unicode characters over codepoint 0xffff
-* https://github.com/yaml/pyyaml/pull/65 -- Support unicode literals over codepoint 0xffff
 * https://github.com/yaml/pyyaml/pull/75 -- add 3.12 changelog
 * https://github.com/yaml/pyyaml/pull/76 -- Fallback to Pure Python if Compilation fails
 * https://github.com/yaml/pyyaml/pull/84 -- Drop unsupported Python 3.3
@@ -25,12 +67,17 @@ For a complete changelog, see:
 * https://github.com/yaml/pyyaml/pull/105 -- Removed Python 2.6 & 3.3 support
 * https://github.com/yaml/pyyaml/pull/111 -- Remove commented out Psyco code
 * https://github.com/yaml/pyyaml/pull/129 -- Remove call to `ord` in lib3 emitter code
-* https://github.com/yaml/pyyaml/pull/143 -- Allow to turn off sorting keys in Dumper
 * https://github.com/yaml/pyyaml/pull/149 -- Test on Python 3.7-dev
 * https://github.com/yaml/pyyaml/pull/158 -- Support escaped slash in double quotes "\/"
+* https://github.com/yaml/pyyaml/pull/175 -- Updated link to pypi in release announcement
 * https://github.com/yaml/pyyaml/pull/181 -- Import Hashable from collections.abc
+* https://github.com/yaml/pyyaml/pull/194 -- Reverting https://github.com/yaml/pyyaml/pull/74
+* https://github.com/yaml/pyyaml/pull/195 -- Build libyaml on travis
+* https://github.com/yaml/pyyaml/pull/196 -- Force cython when building sdist
+* https://github.com/yaml/pyyaml/pull/254 -- Allow to turn off sorting keys in Dumper (2)
 * https://github.com/yaml/pyyaml/pull/256 -- Make default_flow_style=False
 * https://github.com/yaml/pyyaml/pull/257 -- Deprecate yaml.load and add FullLoader and UnsafeLoader classes
+* https://github.com/yaml/pyyaml/pull/261 -- Skip certain unicode tests when maxunicode not > 0xffff
 * https://github.com/yaml/pyyaml/pull/263 -- Windows Appveyor build
 
 3.13 (2018-07-05)
diff --git a/README b/README
index 361839a05..49c87e764 100644
--- a/README
+++ b/README
@@ -15,6 +15,10 @@ parser and emitter as follows:
     >>> yaml.load(stream, Loader=yaml.CLoader)
     >>> yaml.dump(data, Dumper=yaml.CDumper)
 
+If you don't trust the input stream, you should use:
+
+    >>> yaml.safe_load(stream)
+
 PyYAML includes a comprehensive test suite.  To run the tests,
 type 'python setup.py test'.
 
diff --git a/announcement.msg b/announcement.msg
index 99bf92422..c52ecd56a 100644
--- a/announcement.msg
+++ b/announcement.msg
@@ -1,57 +1,36 @@
-From: Ingy döt Net <ingy@ingy.net>
+From: Tina Müller <post@tinita.de>
 To: python-list@python.org, python-announce@python.org, yaml-core@lists.sourceforge.net
-Subject: [ANN] PyYAML-5.1: YAML parser and emitter for Python
+Subject: [ANN] PyYAML-5.3: YAML parser and emitter for Python
 
 =======================
- Announcing PyYAML-5.1
+Announcing PyYAML-5.3
 =======================
 
-A new MAJOR RELEASE of PyYAML is now available:
+A new release of PyYAML is now available:
 https://pypi.org/project/PyYAML/
 
-This is the first major release of PyYAML under the new maintenance team.
-
-Among the many changes listed below, this release specifically addresses the
-arbitrary code execution issue raised by:
-
-    https://nvd.nist.gov/vuln/detail/CVE-2017-18342
-
-(See https://github.com/yaml/pyyaml/wiki/PyYAML-yaml.load(input)-Deprecation
-for complete details).
-
-The PyYAML project is now maintained by the YAML and Python communities.
-Planning happens on the #yaml-dev, #pyyaml and #libyaml IRC channels on
-irc.freenode.net.
-
+This release contains some bugfixes (handling of slots, enable unicode for
+maxunicode < 0xffff, enable large files), enhancements (create timezone
+aware datetimes) and some other small enhancements.
 
 Changes
 =======
 
-* https://github.com/yaml/pyyaml/pull/35  -- Some modernization of the test running
-* https://github.com/yaml/pyyaml/pull/42  -- Install tox in a virtualenv
-* https://github.com/yaml/pyyaml/pull/45  -- Allow colon in a plain scalar in a flow context
-* https://github.com/yaml/pyyaml/pull/48  -- Fix typos
-* https://github.com/yaml/pyyaml/pull/55  -- Improve RepresenterError creation
-* https://github.com/yaml/pyyaml/pull/59  -- Resolves #57, update readme issues link
-* https://github.com/yaml/pyyaml/pull/60  -- Document and test Python 3.6 support
-* https://github.com/yaml/pyyaml/pull/61  -- Use Travis CI built in pip cache support
-* https://github.com/yaml/pyyaml/pull/62  -- Remove tox workaround for Travis CI
-* https://github.com/yaml/pyyaml/pull/63  -- Adding support to Unicode characters over codepoint 0xffff
-* https://github.com/yaml/pyyaml/pull/65  -- Support unicode literals over codepoint 0xffff
-* https://github.com/yaml/pyyaml/pull/75  -- add 3.12 changelog
-* https://github.com/yaml/pyyaml/pull/76  -- Fallback to Pure Python if Compilation fails
-* https://github.com/yaml/pyyaml/pull/84  -- Drop unsupported Python 3.3
-* https://github.com/yaml/pyyaml/pull/102 -- Include license file in the generated wheel package
-* https://github.com/yaml/pyyaml/pull/105 -- Removed Python 2.6 & 3.3 support
-* https://github.com/yaml/pyyaml/pull/111 -- Remove commented out Psyco code
-* https://github.com/yaml/pyyaml/pull/129 -- Remove call to `ord` in lib3 emitter code
-* https://github.com/yaml/pyyaml/pull/143 -- Allow to turn off sorting keys in Dumper
-* https://github.com/yaml/pyyaml/pull/149 -- Test on Python 3.7-dev
-* https://github.com/yaml/pyyaml/pull/158 -- Support escaped slash in double quotes "\/"
-* https://github.com/yaml/pyyaml/pull/181 -- Import Hashable from collections.abc
-* https://github.com/yaml/pyyaml/pull/256 -- Make default_flow_style=False
-* https://github.com/yaml/pyyaml/pull/257 -- Deprecate yaml.load and add FullLoader and UnsafeLoader classes
-* https://github.com/yaml/pyyaml/pull/263 -- Windows Appveyor build
+* https://github.com/yaml/pyyaml/pull/290 -- Use `is` instead of equality for comparing with `None`
+* https://github.com/yaml/pyyaml/pull/270 -- fix typos and stylistic nit
+* https://github.com/yaml/pyyaml/pull/309 -- Fix up small typo
+* https://github.com/yaml/pyyaml/pull/161 -- Fix handling of __slots__
+* https://github.com/yaml/pyyaml/pull/358 -- Allow calling add_multi_constructor with None
+* https://github.com/yaml/pyyaml/pull/285 -- Add use of safe_load() function in README
+* https://github.com/yaml/pyyaml/pull/351 -- Fix reader for Unicode code points over 0xFFFF
+* https://github.com/yaml/pyyaml/pull/360 -- Enable certain unicode tests when maxunicode not > 0xffff
+* https://github.com/yaml/pyyaml/pull/359 -- Use full_load in yaml-highlight example
+* https://github.com/yaml/pyyaml/pull/244 -- Document that PyYAML is implemented with Cython
+* https://github.com/yaml/pyyaml/pull/329 -- Fix for Python 3.10
+* https://github.com/yaml/pyyaml/pull/310 -- increase size of index, line, and column fields
+* https://github.com/yaml/pyyaml/pull/260 -- remove some unused imports
+* https://github.com/yaml/pyyaml/pull/163 -- Create timezone-aware datetimes when parsed as such
+* https://github.com/yaml/pyyaml/pull/363 -- Add tests for timezone
 
 
 Resources
diff --git a/tests/data/emitting-unacceptable-unicode-character-bug-ucs4-py2.code b/emitting-unacceptable-unicode-character-bug.code
similarity index 100%
rename from tests/data/emitting-unacceptable-unicode-character-bug-ucs4-py2.code
rename to emitting-unacceptable-unicode-character-bug.code
diff --git a/tests/data/emitting-unacceptable-unicode-character-bug-ucs4-py2.data b/emitting-unacceptable-unicode-character-bug.data
similarity index 100%
rename from tests/data/emitting-unacceptable-unicode-character-bug-ucs4-py2.data
rename to emitting-unacceptable-unicode-character-bug.data
diff --git a/tests/data/emitting-unacceptable-unicode-character-bug-ucs4-py2.skip-ext b/emitting-unacceptable-unicode-character-bug.skip-ext
similarity index 100%
rename from tests/data/emitting-unacceptable-unicode-character-bug-ucs4-py2.skip-ext
rename to emitting-unacceptable-unicode-character-bug.skip-ext
diff --git a/examples/yaml-highlight/yaml_hl.py b/examples/yaml-highlight/yaml_hl.py
index d6f7bf4eb..96e0ae7b1 100755
--- a/examples/yaml-highlight/yaml_hl.py
+++ b/examples/yaml-highlight/yaml_hl.py
@@ -37,7 +37,7 @@ def __setstate__(self, state):
 class YAMLHighlight:
 
     def __init__(self, options):
-        config = yaml.load(file(options.config, 'rb').read())
+        config = yaml.full_load(file(options.config, 'rb').read())
         self.style = config[options.style]
         if options.input:
             self.input = file(options.input, 'rb')
diff --git a/ext/_yaml.pyx b/ext/_yaml.pyx
index b2f409cc8..ff4efe80b 100644
--- a/ext/_yaml.pyx
+++ b/ext/_yaml.pyx
@@ -63,13 +63,13 @@ MappingNode = yaml.nodes.MappingNode
 
 cdef class Mark:
     cdef readonly object name
-    cdef readonly int index
-    cdef readonly int line
-    cdef readonly int column
+    cdef readonly size_t index
+    cdef readonly size_t line
+    cdef readonly size_t column
     cdef readonly buffer
     cdef readonly pointer
 
-    def __init__(self, object name, int index, int line, int column,
+    def __init__(self, object name, size_t index, size_t line, size_t column,
             object buffer, object pointer):
         self.name = name
         self.index = index
diff --git a/lib/yaml/__init__.py b/lib/yaml/__init__.py
index e7a419dd2..195470479 100644
--- a/lib/yaml/__init__.py
+++ b/lib/yaml/__init__.py
@@ -8,7 +8,7 @@
 from loader import *
 from dumper import *
 
-__version__ = '5.1'
+__version__ = '5.3'
 
 try:
     from cyaml import *
@@ -309,42 +309,62 @@ def safe_dump(data, stream=None, **kwds):
     return dump_all([data], stream, Dumper=SafeDumper, **kwds)
 
 def add_implicit_resolver(tag, regexp, first=None,
-        Loader=Loader, Dumper=Dumper):
+        Loader=None, Dumper=Dumper):
     """
     Add an implicit scalar detector.
     If an implicit scalar value matches the given regexp,
     the corresponding tag is assigned to the scalar.
     first is a sequence of possible initial characters or None.
     """
-    Loader.add_implicit_resolver(tag, regexp, first)
+    if Loader is None:
+        loader.Loader.add_implicit_resolver(tag, regexp, first)
+        loader.FullLoader.add_implicit_resolver(tag, regexp, first)
+        loader.UnsafeLoader.add_implicit_resolver(tag, regexp, first)
+    else:
+        Loader.add_implicit_resolver(tag, regexp, first)
     Dumper.add_implicit_resolver(tag, regexp, first)
 
-def add_path_resolver(tag, path, kind=None, Loader=Loader, Dumper=Dumper):
+def add_path_resolver(tag, path, kind=None, Loader=None, Dumper=Dumper):
     """
     Add a path based resolver for the given tag.
     A path is a list of keys that forms a path
     to a node in the representation tree.
     Keys can be string values, integers, or None.
     """
-    Loader.add_path_resolver(tag, path, kind)
+    if Loader is None:
+        loader.Loader.add_path_resolver(tag, path, kind)
+        loader.FullLoader.add_path_resolver(tag, path, kind)
+        loader.UnsafeLoader.add_path_resolver(tag, path, kind)
+    else:
+        Loader.add_path_resolver(tag, path, kind)
     Dumper.add_path_resolver(tag, path, kind)
 
-def add_constructor(tag, constructor, Loader=Loader):
+def add_constructor(tag, constructor, Loader=None):
     """
     Add a constructor for the given tag.
     Constructor is a function that accepts a Loader instance
     and a node object and produces the corresponding Python object.
     """
-    Loader.add_constructor(tag, constructor)
+    if Loader is None:
+        loader.Loader.add_constructor(tag, constructor)
+        loader.FullLoader.add_constructor(tag, constructor)
+        loader.UnsafeLoader.add_constructor(tag, constructor)
+    else:
+        Loader.add_constructor(tag, constructor)
 
-def add_multi_constructor(tag_prefix, multi_constructor, Loader=Loader):
+def add_multi_constructor(tag_prefix, multi_constructor, Loader=None):
     """
     Add a multi-constructor for the given tag prefix.
     Multi-constructor is called for a node if its tag starts with tag_prefix.
     Multi-constructor accepts a Loader instance, a tag suffix,
     and a node object and produces the corresponding Python object.
     """
-    Loader.add_multi_constructor(tag_prefix, multi_constructor)
+    if Loader is None:
+        loader.Loader.add_multi_constructor(tag_prefix, multi_constructor)
+        loader.FullLoader.add_multi_constructor(tag_prefix, multi_constructor)
+        loader.UnsafeLoader.add_multi_constructor(tag_prefix, multi_constructor)
+    else:
+        Loader.add_multi_constructor(tag_prefix, multi_constructor)
 
 def add_representer(data_type, representer, Dumper=Dumper):
     """
@@ -371,7 +391,12 @@ class YAMLObjectMetaclass(type):
     def __init__(cls, name, bases, kwds):
         super(YAMLObjectMetaclass, cls).__init__(name, bases, kwds)
         if 'yaml_tag' in kwds and kwds['yaml_tag'] is not None:
-            cls.yaml_loader.add_constructor(cls.yaml_tag, cls.from_yaml)
+            if isinstance(cls.yaml_loader, list):
+                for loader in cls.yaml_loader:
+                    loader.add_constructor(cls.yaml_tag, cls.from_yaml)
+            else:
+                cls.yaml_loader.add_constructor(cls.yaml_tag, cls.from_yaml)
+
             cls.yaml_dumper.add_representer(cls, cls.to_yaml)
 
 class YAMLObject(object):
@@ -383,7 +408,7 @@ class YAMLObject(object):
     __metaclass__ = YAMLObjectMetaclass
     __slots__ = ()  # no direct instantiation, so allow immutable subclasses
 
-    yaml_loader = Loader
+    yaml_loader = [Loader, FullLoader, UnsafeLoader]
     yaml_dumper = Dumper
 
     yaml_tag = None
diff --git a/lib/yaml/constructor.py b/lib/yaml/constructor.py
index 516dad1ce..8ce39722d 100644
--- a/lib/yaml/constructor.py
+++ b/lib/yaml/constructor.py
@@ -18,6 +18,29 @@
 class ConstructorError(MarkedYAMLError):
     pass
 
+
+class timezone(datetime.tzinfo):
+    def __init__(self, offset):
+        self._offset = offset
+        seconds = abs(offset).total_seconds()
+        self._name = 'UTC%s%02d:%02d' % (
+            '-' if offset.days < 0 else '+',
+            seconds // 3600,
+            seconds % 3600 // 60
+        )
+
+    def tzname(self, dt=None):
+        return self._name
+
+    def utcoffset(self, dt=None):
+        return self._offset
+
+    def dst(self, dt=None):
+        return datetime.timedelta(0)
+
+    __repr__ = __str__ = tzname
+
+
 class BaseConstructor(object):
 
     yaml_constructors = {}
@@ -74,7 +97,7 @@ def construct_object(self, node, deep=False):
             constructor = self.yaml_constructors[node.tag]
         else:
             for tag_prefix in self.yaml_multi_constructors:
-                if node.tag.startswith(tag_prefix):
+                if tag_prefix is not None and node.tag.startswith(tag_prefix):
                     tag_suffix = node.tag[len(tag_prefix):]
                     constructor = self.yaml_multi_constructors[tag_prefix]
                     break
@@ -293,7 +316,7 @@ def construct_yaml_binary(self, node):
             return str(value).decode('base64')
         except (binascii.Error, UnicodeEncodeError), exc:
             raise ConstructorError(None, None,
-                    "failed to decode base64 data: %s" % exc, node.start_mark) 
+                    "failed to decode base64 data: %s" % exc, node.start_mark)
 
     timestamp_regexp = re.compile(
             ur'''^(?P<year>[0-9][0-9][0-9][0-9])
@@ -320,22 +343,23 @@ def construct_yaml_timestamp(self, node):
         minute = int(values['minute'])
         second = int(values['second'])
         fraction = 0
+        tzinfo = None
         if values['fraction']:
             fraction = values['fraction'][:6]
             while len(fraction) < 6:
                 fraction += '0'
             fraction = int(fraction)
-        delta = None
         if values['tz_sign']:
             tz_hour = int(values['tz_hour'])
             tz_minute = int(values['tz_minute'] or 0)
             delta = datetime.timedelta(hours=tz_hour, minutes=tz_minute)
             if values['tz_sign'] == '-':
                 delta = -delta
-        data = datetime.datetime(year, month, day, hour, minute, second, fraction)
-        if delta:
-            data -= delta
-        return data
+            tzinfo = timezone(delta)
+        elif values['tz']:
+            tzinfo = timezone(datetime.timedelta(0))
+        return datetime.datetime(year, month, day, hour, minute, second, fraction,
+                                 tzinfo=tzinfo)
 
     def construct_yaml_omap(self, node):
         # Note: we do not check for duplicate keys, because it's too
@@ -497,7 +521,7 @@ def find_python_module(self, name, mark, unsafe=False):
             except ImportError, exc:
                 raise ConstructorError("while constructing a Python module", mark,
                         "cannot find module %r (%s)" % (name.encode('utf-8'), exc), mark)
-        if not name in sys.modules:
+        if name not in sys.modules:
             raise ConstructorError("while constructing a Python module", mark,
                     "module %r is not imported" % name.encode('utf-8'), mark)
         return sys.modules[name]
@@ -517,7 +541,7 @@ def find_python_name(self, name, mark, unsafe=False):
             except ImportError, exc:
                 raise ConstructorError("while constructing a Python object", mark,
                         "cannot find module %r (%s)" % (module_name.encode('utf-8'), exc), mark)
-        if not module_name in sys.modules:
+        if module_name not in sys.modules:
             raise ConstructorError("while constructing a Python object", mark,
                     "module %r is not imported" % module_name.encode('utf-8'), mark)
         module = sys.modules[module_name]
@@ -578,7 +602,7 @@ def set_python_instance_state(self, instance, state):
             elif state:
                 slotstate.update(state)
             for key, value in slotstate.items():
-                setattr(object, key, value)
+                setattr(instance, key, value)
 
     def construct_python_object(self, suffix, node):
         # Format:
@@ -683,10 +707,6 @@ def construct_python_object_new(self, suffix, node):
     u'tag:yaml.org,2002:python/object:',
     FullConstructor.construct_python_object)
 
-FullConstructor.add_multi_constructor(
-    u'tag:yaml.org,2002:python/object/apply:',
-    FullConstructor.construct_python_object_apply)
-
 FullConstructor.add_multi_constructor(
     u'tag:yaml.org,2002:python/object/new:',
     FullConstructor.construct_python_object_new)
@@ -703,6 +723,10 @@ def make_python_instance(self, suffix, node, args=None, kwds=None, newobj=False)
         return super(UnsafeConstructor, self).make_python_instance(
             suffix, node, args, kwds, newobj, unsafe=True)
 
+UnsafeConstructor.add_multi_constructor(
+    u'tag:yaml.org,2002:python/object/apply:',
+    UnsafeConstructor.construct_python_object_apply)
+
 # Constructor is same as UnsafeConstructor. Need to leave this in place in case
 # people have extended it directly.
 class Constructor(UnsafeConstructor):
diff --git a/lib/yaml/emitter.py b/lib/yaml/emitter.py
index 9561a8274..23c25ca80 100644
--- a/lib/yaml/emitter.py
+++ b/lib/yaml/emitter.py
@@ -706,7 +706,7 @@ def analyze_scalar(self, scalar):
             if not (ch == u'\n' or u'\x20' <= ch <= u'\x7E'):
                 if (ch == u'\x85' or u'\xA0' <= ch <= u'\uD7FF'
                         or u'\uE000' <= ch <= u'\uFFFD'
-                        or ((not has_ucs4) or (u'\U00010000' <= ch < u'\U0010ffff'))) and ch != u'\uFEFF':
+                        or (u'\U00010000' <= ch < u'\U0010ffff')) and ch != u'\uFEFF':
                     unicode_characters = True
                     if not self.allow_unicode:
                         special_characters = True
diff --git a/lib/yaml/loader.py b/lib/yaml/loader.py
index a79182eaf..4d773c3cc 100644
--- a/lib/yaml/loader.py
+++ b/lib/yaml/loader.py
@@ -51,7 +51,7 @@ def __init__(self, stream):
 # UnsafeLoader is the same as Loader (which is and was always unsafe on
 # untrusted input). Use of either Loader or UnsafeLoader should be rare, since
 # FullLoad should be able to load almost all YAML safely. Loader is left intact
-# to ensure backwards compatability.
+# to ensure backwards compatibility.
 class UnsafeLoader(Reader, Scanner, Parser, Composer, Constructor, Resolver):
 
     def __init__(self, stream):
diff --git a/lib/yaml/reader.py b/lib/yaml/reader.py
index b2f10b091..4b377d61e 100644
--- a/lib/yaml/reader.py
+++ b/lib/yaml/reader.py
@@ -139,7 +139,7 @@ def determine_encoding(self):
     if has_ucs4:
         NON_PRINTABLE = re.compile(u'[^\x09\x0A\x0D\x20-\x7E\x85\xA0-\uD7FF\uE000-\uFFFD\U00010000-\U0010ffff]')
     else:
-        NON_PRINTABLE = re.compile(u'[^\x09\x0A\x0D\x20-\x7E\x85\xA0-\uD7FF\uE000-\uFFFD]')
+        NON_PRINTABLE = re.compile(u'[^\x09\x0A\x0D\x20-\x7E\x85\xA0-\uFFFD]|(?:^|[^\uD800-\uDBFF])[\uDC00-\uDFFF]|[\uD800-\uDBFF](?:[^\uDC00-\uDFFF]|$)')
     def check_printable(self, data):
         match = self.NON_PRINTABLE.search(data)
         if match:
diff --git a/lib/yaml/representer.py b/lib/yaml/representer.py
index 9dca41af7..93e09b67b 100644
--- a/lib/yaml/representer.py
+++ b/lib/yaml/representer.py
@@ -3,11 +3,12 @@
     'RepresenterError']
 
 from error import *
+
 from nodes import *
 
 import datetime
 
-import sys, copy_reg, types
+import copy_reg, types
 
 class RepresenterError(YAMLError):
     pass
diff --git a/lib/yaml/scanner.py b/lib/yaml/scanner.py
index 5126cf07b..098ea7be8 100644
--- a/lib/yaml/scanner.py
+++ b/lib/yaml/scanner.py
@@ -332,7 +332,7 @@ def unwind_indent(self, column):
         ## }
         #if self.flow_level and self.indent > column:
         #    raise ScannerError(None, None,
-        #            "invalid intendation or unclosed '[' or '{'",
+        #            "invalid indentation or unclosed '[' or '{'",
         #            self.get_mark())
 
         # In the flow context, indentation is ignored. We make the scanner less
@@ -370,7 +370,7 @@ def fetch_stream_start(self):
 
     def fetch_stream_end(self):
 
-        # Set the current intendation to -1.
+        # Set the current indentation to -1.
         self.unwind_indent(-1)
 
         # Reset simple keys.
@@ -389,7 +389,7 @@ def fetch_stream_end(self):
 
     def fetch_directive(self):
         
-        # Set the current intendation to -1.
+        # Set the current indentation to -1.
         self.unwind_indent(-1)
 
         # Reset simple keys.
@@ -407,7 +407,7 @@ def fetch_document_end(self):
 
     def fetch_document_indicator(self, TokenClass):
 
-        # Set the current intendation to -1.
+        # Set the current indentation to -1.
         self.unwind_indent(-1)
 
         # Reset simple keys. Note that there could not be a block collection
diff --git a/lib3/yaml/__init__.py b/lib3/yaml/__init__.py
index 5df0bb5fd..658a08a6b 100644
--- a/lib3/yaml/__init__.py
+++ b/lib3/yaml/__init__.py
@@ -8,7 +8,7 @@
 from .loader import *
 from .dumper import *
 
-__version__ = '5.1'
+__version__ = '5.3'
 try:
     from .cyaml import *
     __with_libyaml__ = True
@@ -306,42 +306,62 @@ def safe_dump(data, stream=None, **kwds):
     return dump_all([data], stream, Dumper=SafeDumper, **kwds)
 
 def add_implicit_resolver(tag, regexp, first=None,
-        Loader=Loader, Dumper=Dumper):
+        Loader=None, Dumper=Dumper):
     """
     Add an implicit scalar detector.
     If an implicit scalar value matches the given regexp,
     the corresponding tag is assigned to the scalar.
     first is a sequence of possible initial characters or None.
     """
-    Loader.add_implicit_resolver(tag, regexp, first)
+    if Loader is None:
+        loader.Loader.add_implicit_resolver(tag, regexp, first)
+        loader.FullLoader.add_implicit_resolver(tag, regexp, first)
+        loader.UnsafeLoader.add_implicit_resolver(tag, regexp, first)
+    else:
+        Loader.add_implicit_resolver(tag, regexp, first)
     Dumper.add_implicit_resolver(tag, regexp, first)
 
-def add_path_resolver(tag, path, kind=None, Loader=Loader, Dumper=Dumper):
+def add_path_resolver(tag, path, kind=None, Loader=None, Dumper=Dumper):
     """
     Add a path based resolver for the given tag.
     A path is a list of keys that forms a path
     to a node in the representation tree.
     Keys can be string values, integers, or None.
     """
-    Loader.add_path_resolver(tag, path, kind)
+    if Loader is None:
+        loader.Loader.add_path_resolver(tag, path, kind)
+        loader.FullLoader.add_path_resolver(tag, path, kind)
+        loader.UnsafeLoader.add_path_resolver(tag, path, kind)
+    else:
+        Loader.add_path_resolver(tag, path, kind)
     Dumper.add_path_resolver(tag, path, kind)
 
-def add_constructor(tag, constructor, Loader=Loader):
+def add_constructor(tag, constructor, Loader=None):
     """
     Add a constructor for the given tag.
     Constructor is a function that accepts a Loader instance
     and a node object and produces the corresponding Python object.
     """
-    Loader.add_constructor(tag, constructor)
+    if Loader is None:
+        loader.Loader.add_constructor(tag, constructor)
+        loader.FullLoader.add_constructor(tag, constructor)
+        loader.UnsafeLoader.add_constructor(tag, constructor)
+    else:
+        Loader.add_constructor(tag, constructor)
 
-def add_multi_constructor(tag_prefix, multi_constructor, Loader=Loader):
+def add_multi_constructor(tag_prefix, multi_constructor, Loader=None):
     """
     Add a multi-constructor for the given tag prefix.
     Multi-constructor is called for a node if its tag starts with tag_prefix.
     Multi-constructor accepts a Loader instance, a tag suffix,
     and a node object and produces the corresponding Python object.
     """
-    Loader.add_multi_constructor(tag_prefix, multi_constructor)
+    if Loader is None:
+        loader.Loader.add_multi_constructor(tag_prefix, multi_constructor)
+        loader.FullLoader.add_multi_constructor(tag_prefix, multi_constructor)
+        loader.UnsafeLoader.add_multi_constructor(tag_prefix, multi_constructor)
+    else:
+        Loader.add_multi_constructor(tag_prefix, multi_constructor)
 
 def add_representer(data_type, representer, Dumper=Dumper):
     """
@@ -368,7 +388,12 @@ class YAMLObjectMetaclass(type):
     def __init__(cls, name, bases, kwds):
         super(YAMLObjectMetaclass, cls).__init__(name, bases, kwds)
         if 'yaml_tag' in kwds and kwds['yaml_tag'] is not None:
-            cls.yaml_loader.add_constructor(cls.yaml_tag, cls.from_yaml)
+            if isinstance(cls.yaml_loader, list):
+                for loader in cls.yaml_loader:
+                    loader.add_constructor(cls.yaml_tag, cls.from_yaml)
+            else:
+                cls.yaml_loader.add_constructor(cls.yaml_tag, cls.from_yaml)
+
             cls.yaml_dumper.add_representer(cls, cls.to_yaml)
 
 class YAMLObject(metaclass=YAMLObjectMetaclass):
@@ -379,7 +404,7 @@ class YAMLObject(metaclass=YAMLObjectMetaclass):
 
     __slots__ = ()  # no direct instantiation, so allow immutable subclasses
 
-    yaml_loader = Loader
+    yaml_loader = [Loader, FullLoader, UnsafeLoader]
     yaml_dumper = Dumper
 
     yaml_tag = None
diff --git a/lib3/yaml/constructor.py b/lib3/yaml/constructor.py
index 34fc1ae92..cd9167eaf 100644
--- a/lib3/yaml/constructor.py
+++ b/lib3/yaml/constructor.py
@@ -72,7 +72,7 @@ def construct_object(self, node, deep=False):
             constructor = self.yaml_constructors[node.tag]
         else:
             for tag_prefix in self.yaml_multi_constructors:
-                if node.tag.startswith(tag_prefix):
+                if tag_prefix is not None and node.tag.startswith(tag_prefix):
                     tag_suffix = node.tag[len(tag_prefix):]
                     constructor = self.yaml_multi_constructors[tag_prefix]
                     break
@@ -324,22 +324,23 @@ def construct_yaml_timestamp(self, node):
         minute = int(values['minute'])
         second = int(values['second'])
         fraction = 0
+        tzinfo = None
         if values['fraction']:
             fraction = values['fraction'][:6]
             while len(fraction) < 6:
                 fraction += '0'
             fraction = int(fraction)
-        delta = None
         if values['tz_sign']:
             tz_hour = int(values['tz_hour'])
             tz_minute = int(values['tz_minute'] or 0)
             delta = datetime.timedelta(hours=tz_hour, minutes=tz_minute)
             if values['tz_sign'] == '-':
                 delta = -delta
-        data = datetime.datetime(year, month, day, hour, minute, second, fraction)
-        if delta:
-            data -= delta
-        return data
+            tzinfo = datetime.timezone(delta)
+        elif values['tz']:
+            tzinfo = datetime.timezone.utc
+        return datetime.datetime(year, month, day, hour, minute, second, fraction,
+                                 tzinfo=tzinfo)
 
     def construct_yaml_omap(self, node):
         # Note: we do not check for duplicate keys, because it's too
@@ -513,7 +514,7 @@ def find_python_module(self, name, mark, unsafe=False):
             except ImportError as exc:
                 raise ConstructorError("while constructing a Python module", mark,
                         "cannot find module %r (%s)" % (name, exc), mark)
-        if not name in sys.modules:
+        if name not in sys.modules:
             raise ConstructorError("while constructing a Python module", mark,
                     "module %r is not imported" % name, mark)
         return sys.modules[name]
@@ -533,7 +534,7 @@ def find_python_name(self, name, mark, unsafe=False):
             except ImportError as exc:
                 raise ConstructorError("while constructing a Python object", mark,
                         "cannot find module %r (%s)" % (module_name, exc), mark)
-        if not module_name in sys.modules:
+        if module_name not in sys.modules:
             raise ConstructorError("while constructing a Python object", mark,
                     "module %r is not imported" % module_name, mark)
         module = sys.modules[module_name]
@@ -585,7 +586,7 @@ def set_python_instance_state(self, instance, state):
             elif state:
                 slotstate.update(state)
             for key, value in slotstate.items():
-                setattr(object, key, value)
+                setattr(instance, key, value)
 
     def construct_python_object(self, suffix, node):
         # Format:
@@ -694,10 +695,6 @@ def construct_python_object_new(self, suffix, node):
     'tag:yaml.org,2002:python/object:',
     FullConstructor.construct_python_object)
 
-FullConstructor.add_multi_constructor(
-    'tag:yaml.org,2002:python/object/apply:',
-    FullConstructor.construct_python_object_apply)
-
 FullConstructor.add_multi_constructor(
     'tag:yaml.org,2002:python/object/new:',
     FullConstructor.construct_python_object_new)
@@ -714,6 +711,10 @@ def make_python_instance(self, suffix, node, args=None, kwds=None, newobj=False)
         return super(UnsafeConstructor, self).make_python_instance(
             suffix, node, args, kwds, newobj, unsafe=True)
 
+UnsafeConstructor.add_multi_constructor(
+    'tag:yaml.org,2002:python/object/apply:',
+    UnsafeConstructor.construct_python_object_apply)
+
 # Constructor is same as UnsafeConstructor. Need to leave this in place in case
 # people have extended it directly.
 class Constructor(UnsafeConstructor):
diff --git a/lib3/yaml/loader.py b/lib3/yaml/loader.py
index 414cb2c15..e90c11224 100644
--- a/lib3/yaml/loader.py
+++ b/lib3/yaml/loader.py
@@ -51,7 +51,7 @@ def __init__(self, stream):
 # UnsafeLoader is the same as Loader (which is and was always unsafe on
 # untrusted input). Use of either Loader or UnsafeLoader should be rare, since
 # FullLoad should be able to load almost all YAML safely. Loader is left intact
-# to ensure backwards compatability.
+# to ensure backwards compatibility.
 class UnsafeLoader(Reader, Scanner, Parser, Composer, Constructor, Resolver):
 
     def __init__(self, stream):
diff --git a/lib3/yaml/representer.py b/lib3/yaml/representer.py
index dd144017b..3b0b192ef 100644
--- a/lib3/yaml/representer.py
+++ b/lib3/yaml/representer.py
@@ -5,7 +5,7 @@
 from .error import *
 from .nodes import *
 
-import datetime, sys, copyreg, types, base64, collections
+import datetime, copyreg, types, base64, collections
 
 class RepresenterError(YAMLError):
     pass
diff --git a/lib3/yaml/scanner.py b/lib3/yaml/scanner.py
index 775dbcc6d..7437ede1c 100644
--- a/lib3/yaml/scanner.py
+++ b/lib3/yaml/scanner.py
@@ -332,7 +332,7 @@ def unwind_indent(self, column):
         ## }
         #if self.flow_level and self.indent > column:
         #    raise ScannerError(None, None,
-        #            "invalid intendation or unclosed '[' or '{'",
+        #            "invalid indentation or unclosed '[' or '{'",
         #            self.get_mark())
 
         # In the flow context, indentation is ignored. We make the scanner less
@@ -370,7 +370,7 @@ def fetch_stream_start(self):
 
     def fetch_stream_end(self):
 
-        # Set the current intendation to -1.
+        # Set the current indentation to -1.
         self.unwind_indent(-1)
 
         # Reset simple keys.
@@ -389,7 +389,7 @@ def fetch_stream_end(self):
 
     def fetch_directive(self):
         
-        # Set the current intendation to -1.
+        # Set the current indentation to -1.
         self.unwind_indent(-1)
 
         # Reset simple keys.
@@ -407,7 +407,7 @@ def fetch_document_end(self):
 
     def fetch_document_indicator(self, TokenClass):
 
-        # Set the current intendation to -1.
+        # Set the current indentation to -1.
         self.unwind_indent(-1)
 
         # Reset simple keys. Note that there could not be a block collection
diff --git a/packaging/build/appveyor.ps1 b/packaging/build/appveyor.ps1
index a9e6ad289..a60d0bbb2 100644
--- a/packaging/build/appveyor.ps1
+++ b/packaging/build/appveyor.ps1
@@ -5,17 +5,25 @@
 # TODO: get version number from setup.py and/or lib(3)/__version__
 # Update-AppveyorBuild -Version $dynamic_version
 
-Function Bootstrap() {
-    # uncomment when we want to start testing on Python 3.8
-    # ensure py38 is present (current Appveyor VS2015 image doesn't include it)
-    #If(-not $(Test-Path C:\Python38)) {
-    #    choco.exe install python3 --version=3.8.0-a2 --forcex86 --force #--install-arguments="TargetDir=C:\Python38 PrependPath=0" --no-progress
-    #}
+Function Invoke-Exe([scriptblock]$sb) {
+    & $sb
+    $exitcode = $LASTEXITCODE
+    If($exitcode -ne 0) {
+       throw "exe failed with nonzero exit code $exitcode"
+    }
+}
 
-    #If(-not $(Test-Path C:\Python38-x64)) {
-    #    choco.exe install python3 --version=3.8.0-a2 --force #--install-arguments="TargetDir=C:\Python38-x64 PrependPath=0" --no-progress
-    #}
+Function Bootstrap() {
+<#
+    # ensure python 3.9 prerelease is present (current Appveyor VS2015 image doesn't include it)
+    If(-not $(Test-Path C:\Python39)) {
+        Invoke-Exe { choco.exe install python3 --version=3.9.0-a1 --forcex86 --force --params="/InstallDir:C:\Python39" --no-progress }
+    }
 
+    If(-not $(Test-Path C:\Python39-x64)) {
+        Invoke-Exe { choco.exe install python3 --version=3.9.0-a1 --force --params="/InstallDir:C:\Python39-x64" --no-progress }
+    }
+#>
     Write-Output "patching Windows SDK bits for distutils"
 
     # patch 7.0/7.1 vcvars SDK bits up to work with distutils query
@@ -23,11 +31,7 @@ Function Bootstrap() {
     Set-Content -Path 'C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\bin\amd64\vcvars64.bat' '@CALL "C:\Program Files\Microsoft SDKs\Windows\v7.1\Bin\SetEnv.cmd" /Release /x64'
 
     # patch VS9 x64 CMake config for VS Express, hide `reg.exe` stderr noise
-    $noise = reg.exe import packaging\build\FixVS9CMake.reg 2>&1
-
-    If($LASTEXITCODE -ne 0) {
-        throw "reg failed with error code $LASTEXITCODE"
-    }
+    Invoke-Exe { $noise = reg.exe import packaging\build\FixVS9CMake.reg 2>&1 }
 
     Copy-Item -Path "C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\vcpackages\AMD64.VCPlatform.config" -Destination "C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\vcpackages\AMD64.VCPlatform.Express.config" -Force
     Copy-Item -Path "C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\vcpackages\Itanium.VCPlatform.config" -Destination "C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\vcpackages\Itanium.VCPlatform.Express.config" -Force
@@ -41,7 +45,7 @@ Function Bootstrap() {
     Write-Output "cloning libyaml from $libyaml_repo_url / $libyaml_refspec"
 
     If(-not $(Test-Path .\libyaml)) {
-        git clone -b $libyaml_refspec $libyaml_repo_url 2>&1
+        Invoke-Exe { git clone -b $libyaml_refspec $libyaml_repo_url 2>&1 }
     }
 }
 
@@ -53,7 +57,7 @@ Function Build-Wheel($python_path) {
     Write-Output "building pyyaml wheel for $python_path"
 
     # query distutils for the VC version used to build this Python; translate to a VS version to choose the right generator
-    $python_vs_buildver = & $python -c "from distutils.version import LooseVersion; from distutils.msvc9compiler import get_build_version; print(LooseVersion(str(get_build_version())).version[0])"
+    $python_vs_buildver = Invoke-Exe { & $python -c "from distutils.version import LooseVersion; from distutils.msvc9compiler import get_build_version; print(LooseVersion(str(get_build_version())).version[0])" }
 
     $python_cmake_generator = switch($python_vs_buildver) {
         "9" { "Visual Studio 9 2008" }
@@ -63,7 +67,7 @@ Function Build-Wheel($python_path) {
     }
 
     # query arch this python was built for
-    $python_arch = & $python -c "from distutils.util import get_platform; print(str(get_platform()))"
+    $python_arch = Invoke-Exe { & $python -c "from distutils.util import get_platform; print(str(get_platform()))" }
 
     if($python_arch -eq 'win-amd64') {
         $python_cmake_generator += " Win64"
@@ -71,7 +75,7 @@ Function Build-Wheel($python_path) {
     }
 
     # snarf VS vars (paths, etc) for the matching VS version and arch that built this Python
-    $raw_vars_out = & cmd.exe /c "`"C:\Program Files (x86)\Microsoft Visual Studio $($python_vs_buildver).0\VC\vcvarsall.bat`" $vcvars_arch & set"
+    $raw_vars_out = Invoke-Exe { cmd.exe /c "`"C:\Program Files (x86)\Microsoft Visual Studio $($python_vs_buildver).0\VC\vcvarsall.bat`" $vcvars_arch & set" }
     foreach($kv in $raw_vars_out) {
         If($kv -match "=") {
             $kv = $kv.Split("=", 2)
@@ -83,23 +87,23 @@ Function Build-Wheel($python_path) {
     }
 
     # ensure pip is current (some appveyor pips are not)
-    & $python -W "ignore:DEPRECATION" -m pip install --upgrade pip
+    Invoke-Exe { & $python -W "ignore:DEPRECATION" -m pip install --upgrade pip }
 
     # ensure required-for-build packages are present and up-to-date
-    & $python -W "ignore:DEPRECATION" -m pip install --upgrade cython wheel setuptools --no-warn-script-location
+    Invoke-Exe { & $python -W "ignore:DEPRECATION" -m pip install --upgrade cython wheel setuptools --no-warn-script-location }
 
     pushd libyaml
-    git clean -fdx
+    Invoke-Exe { git clean -fdx }
     popd
 
     mkdir libyaml\build
 
     pushd libyaml\build
-    cmake.exe -G $python_cmake_generator -DYAML_STATIC_LIB_NAME=yaml ..
-    cmake.exe --build . --config Release
+    Invoke-Exe { cmake.exe -G $python_cmake_generator -DYAML_STATIC_LIB_NAME=yaml .. }
+    Invoke-Exe { cmake.exe --build . --config Release }
     popd
 
-    & $python setup.py --with-libyaml build_ext -I libyaml\include -L libyaml\build\Release -D YAML_DECLARE_STATIC build test bdist_wheel
+    Invoke-Exe { & $python setup.py --with-libyaml build_ext -I libyaml\include -L libyaml\build\Release -D YAML_DECLARE_STATIC build test bdist_wheel }
 }
 
 Function Upload-Artifacts() {
@@ -115,14 +119,14 @@ Bootstrap
 $pythons = @(
 "C:\Python27"
 "C:\Python27-x64"
-"C:\Python34"
-"C:\Python34-x64"
 "C:\Python35"
 "C:\Python35-x64"
 "C:\Python36"
 "C:\Python36-x64"
 "C:\Python37"
 "C:\Python37-x64"
+"C:\Python38"
+"C:\Python38-x64"
 )
 
 #$pythons = @("C:\$($env:PYTHON_VER)")
diff --git a/setup.py b/setup.py
index e21ce9f73..1a0413a94 100644
--- a/setup.py
+++ b/setup.py
@@ -1,6 +1,6 @@
 
 NAME = 'PyYAML'
-VERSION = '5.1'
+VERSION = '5.3'
 DESCRIPTION = "YAML parser and emitter for Python"
 LONG_DESCRIPTION = """\
 YAML is a data serialization format designed for human readability
@@ -25,14 +25,15 @@
     "Intended Audience :: Developers",
     "License :: OSI Approved :: MIT License",
     "Operating System :: OS Independent",
+    "Programming Language :: Cython",
     "Programming Language :: Python",
     "Programming Language :: Python :: 2",
     "Programming Language :: Python :: 2.7",
     "Programming Language :: Python :: 3",
-    "Programming Language :: Python :: 3.4",
     "Programming Language :: Python :: 3.5",
     "Programming Language :: Python :: 3.6",
     "Programming Language :: Python :: 3.7",
+    "Programming Language :: Python :: 3.8",
     "Programming Language :: Python :: Implementation :: CPython",
     "Programming Language :: Python :: Implementation :: PyPy",
     "Topic :: Software Development :: Libraries :: Python Modules",
@@ -64,7 +65,6 @@
 from distutils.core import setup, Command
 from distutils.core import Distribution as _Distribution
 from distutils.core import Extension as _Extension
-from distutils.dir_util import mkpath
 from distutils.command.build_ext import build_ext as _build_ext
 from distutils.command.bdist_rpm import bdist_rpm as _bdist_rpm
 from distutils.errors import DistutilsError, CompileError, LinkError, DistutilsPlatformError
@@ -311,5 +311,5 @@ def run(self):
 
         distclass=Distribution,
         cmdclass=cmdclass,
-        python_requires='>=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*',
+        python_requires='>=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*',
     )
diff --git a/tests/data/construct-python-object.code b/tests/data/construct-python-object.code
index 7f1edf125..9e611e43a 100644
--- a/tests/data/construct-python-object.code
+++ b/tests/data/construct-python-object.code
@@ -17,6 +17,8 @@ NewArgsWithState(1, 'two', [3,3,3]),
 Reduce(1, 'two', [3,3,3]),
 ReduceWithState(1, 'two', [3,3,3]),
 
+Slots(1, 'two', [3,3,3]),
+
 MyInt(3),
 MyList(3),
 MyDict(3),
diff --git a/tests/data/construct-python-object.data b/tests/data/construct-python-object.data
index bce8b2ed3..66797e4c9 100644
--- a/tests/data/construct-python-object.data
+++ b/tests/data/construct-python-object.data
@@ -16,6 +16,8 @@
 - !!python/object/apply:test_constructor.Reduce [1, two, [3,3,3]]
 - !!python/object/apply:test_constructor.ReduceWithState { args: [1, two], state: [3,3,3] }
 
+- !!python/object/new:test_constructor.Slots { state: !!python/tuple [null, { foo: 1, bar: 'two', baz: [3,3,3] } ] }
+
 - !!python/object/new:test_constructor.MyInt [3]
 - !!python/object/new:test_constructor.MyList { listitems: [~, ~, ~] }
 - !!python/object/new:test_constructor.MyDict { dictitems: {0, 1, 2} }
diff --git a/tests/data/emoticons-ucs4-.unicode b/tests/data/emoticons.unicode
similarity index 100%
rename from tests/data/emoticons-ucs4-.unicode
rename to tests/data/emoticons.unicode
diff --git a/tests/data/emoticons2-ucs4-.unicode b/tests/data/emoticons2.unicode
similarity index 100%
rename from tests/data/emoticons2-ucs4-.unicode
rename to tests/data/emoticons2.unicode
diff --git a/tests/data/multi-constructor.code b/tests/data/multi-constructor.code
new file mode 100644
index 000000000..590d852a7
--- /dev/null
+++ b/tests/data/multi-constructor.code
@@ -0,0 +1,4 @@
+[
+    {'Tag1': ['a', 1, 'b', 2]},
+    {'Tag2': ['a', 1, 'b', 2]},
+]
diff --git a/tests/data/multi-constructor.multi b/tests/data/multi-constructor.multi
new file mode 100644
index 000000000..4f5d71f42
--- /dev/null
+++ b/tests/data/multi-constructor.multi
@@ -0,0 +1,3 @@
+---
+- !Tag1 [a, 1, b, 2]
+- !!Tag2 [a, 1, b, 2]
diff --git a/tests/data/timestamp-bugs.code b/tests/data/timestamp-bugs.code
index b1d6e9c4f..e2c84cc3c 100644
--- a/tests/data/timestamp-bugs.code
+++ b/tests/data/timestamp-bugs.code
@@ -1,8 +1,8 @@
 [
-    datetime.datetime(2001, 12, 15, 3, 29, 43, 100000),
-    datetime.datetime(2001, 12, 14, 16, 29, 43, 100000),
-    datetime.datetime(2001, 12, 14, 21, 59, 43, 1010),
-    datetime.datetime(2001, 12, 14, 21, 59, 43, 0, FixedOffset(60, "+1")),
-    datetime.datetime(2001, 12, 14, 21, 59, 43, 0, FixedOffset(-90, "-1:30")),
-    datetime.datetime(2005, 7, 8, 17, 35, 4, 517600),
+    [datetime.datetime(2001, 12, 15, 3, 29, 43, 100000), 'UTC-05:30'],
+    [datetime.datetime(2001, 12, 14, 16, 29, 43, 100000), 'UTC+05:30'],
+    [datetime.datetime(2001, 12, 14, 21, 59, 43, 1010), None],
+    [datetime.datetime(2001, 12, 14, 21, 59, 43, 0, FixedOffset(60, "+1")), 'UTC+01:00'],
+    [datetime.datetime(2001, 12, 14, 21, 59, 43, 0, FixedOffset(-90, "-1:30")), 'UTC-01:30'],
+    [datetime.datetime(2005, 7, 8, 17, 35, 4, 517600), None],
 ]
diff --git a/tests/data/timestamp-bugs.data b/tests/data/timestamp-bugs.data
index 721d29082..b243d0d2c 100644
--- a/tests/data/timestamp-bugs.data
+++ b/tests/data/timestamp-bugs.data
@@ -1,6 +1,12 @@
-- 2001-12-14 21:59:43.10 -5:30
-- 2001-12-14 21:59:43.10 +5:30
-- 2001-12-14 21:59:43.00101
-- 2001-12-14 21:59:43+1
-- 2001-12-14 21:59:43-1:30
-- 2005-07-08 17:35:04.517600
+- !MyTime
+  - 2001-12-14 21:59:43.10 -5:30
+- !MyTime
+  - 2001-12-14 21:59:43.10 +5:30
+- !MyTime
+  - 2001-12-14 21:59:43.00101
+- !MyTime
+  - 2001-12-14 21:59:43+1
+- !MyTime
+  - 2001-12-14 21:59:43-1:30
+- !MyTime
+  - 2005-07-08 17:35:04.517600
diff --git a/tests/lib/test_build.py b/tests/lib/test_build.py
index 901e8ed6c..df3f943ba 100644
--- a/tests/lib/test_build.py
+++ b/tests/lib/test_build.py
@@ -2,7 +2,7 @@
 if __name__ == '__main__':
     import sys, os, distutils.util
     build_lib = 'build/lib'
-    build_lib_ext = os.path.join('build', 'lib.%s-%s' % (distutils.util.get_platform(), sys.version[0:3]))
+    build_lib_ext = os.path.join('build', 'lib.{}-{}.{}'.format(distutils.util.get_platform(), *sys.version_info))
     sys.path.insert(0, build_lib)
     sys.path.insert(0, build_lib_ext)
     import test_yaml, test_appliance
diff --git a/tests/lib/test_build_ext.py b/tests/lib/test_build_ext.py
index ff195d519..fa843f6e4 100644
--- a/tests/lib/test_build_ext.py
+++ b/tests/lib/test_build_ext.py
@@ -3,7 +3,7 @@
 if __name__ == '__main__':
     import sys, os, distutils.util
     build_lib = 'build/lib'
-    build_lib_ext = os.path.join('build', 'lib.%s-%s' % (distutils.util.get_platform(), sys.version[0:3]))
+    build_lib_ext = os.path.join('build', 'lib.{}-{}.{}'.format(distutils.util.get_platform(), *sys.version_info))
     sys.path.insert(0, build_lib)
     sys.path.insert(0, build_lib_ext)
     import test_yaml_ext, test_appliance
diff --git a/tests/lib/test_constructor.py b/tests/lib/test_constructor.py
index beee7b0a7..a22fd1891 100644
--- a/tests/lib/test_constructor.py
+++ b/tests/lib/test_constructor.py
@@ -16,7 +16,7 @@ def execute(code):
 def _make_objects():
     global MyLoader, MyDumper, MyTestClass1, MyTestClass2, MyTestClass3, YAMLObject1, YAMLObject2,  \
             AnObject, AnInstance, AState, ACustomState, InitArgs, InitArgsWithState,    \
-            NewArgs, NewArgsWithState, Reduce, ReduceWithState, MyInt, MyList, MyDict,  \
+            NewArgs, NewArgsWithState, Reduce, ReduceWithState, Slots, MyInt, MyList, MyDict,  \
             FixedOffset, today, execute
 
     class MyLoader(yaml.Loader):
@@ -41,7 +41,18 @@ def construct1(constructor, node):
     def represent1(representer, native):
         return representer.represent_mapping("!tag1", native.__dict__)
 
+    def my_time_constructor(constructor, node):
+        seq = constructor.construct_sequence(node)
+        dt = seq[0]
+        tz = None
+        try:
+            tz = dt.tzinfo.tzname(dt)
+        except:
+            pass
+        return [dt, tz]
+
     yaml.add_constructor("!tag1", construct1, Loader=MyLoader)
+    yaml.add_constructor("!MyTime", my_time_constructor, Loader=MyLoader)
     yaml.add_representer(MyTestClass1, represent1, Dumper=MyDumper)
 
     class MyTestClass2(MyTestClass1, yaml.YAMLObject):
@@ -185,6 +196,17 @@ def __reduce__(self):
         def __setstate__(self, state):
             self.baz = state
 
+    class Slots(object):
+        __slots__ = ("foo", "bar", "baz")
+        def __init__(self, foo=None, bar=None, baz=None):
+            self.foo = foo
+            self.bar = bar
+            self.baz = baz
+
+        def __eq__(self, other):
+            return type(self) is type(other) and \
+                (self.foo, self.bar, self.baz) == (other.foo, other.bar, other.baz)
+
     class MyInt(int):
         def __eq__(self, other):
             return type(self) is type(other) and int(self) == int(other)
diff --git a/tests/lib/test_multi_constructor.py b/tests/lib/test_multi_constructor.py
new file mode 100644
index 000000000..f6e28fe0e
--- /dev/null
+++ b/tests/lib/test_multi_constructor.py
@@ -0,0 +1,63 @@
+import yaml
+import pprint
+import sys
+
+def _load_code(expression):
+    return eval(expression)
+
+def myconstructor1(constructor, tag, node):
+    seq = constructor.construct_sequence(node)
+    return {tag: seq }
+
+def myconstructor2(constructor, tag, node):
+    seq = constructor.construct_sequence(node)
+    string = ''
+    try:
+        i = tag.index('!') + 1
+    except:
+        try:
+            i = tag.rindex(':') + 1
+        except:
+            pass
+    if i >= 0:
+        tag = tag[i:]
+    return { tag: seq }
+
+class Multi1(yaml.FullLoader):
+    pass
+class Multi2(yaml.FullLoader):
+    pass
+
+def test_multi_constructor(input_filename, code_filename, verbose=False):
+    input = open(input_filename, 'rb').read().decode('utf-8')
+    native = _load_code(open(code_filename, 'rb').read())
+
+    # default multi constructor for ! and !! tags
+    Multi1.add_multi_constructor('!', myconstructor1)
+    Multi1.add_multi_constructor('tag:yaml.org,2002:', myconstructor1)
+
+    data = yaml.load(input, Loader=Multi1)
+    if verbose:
+        print('Multi1:')
+        print(data)
+        print(native)
+    assert(data == native)
+
+
+    # default multi constructor for all tags
+    Multi2.add_multi_constructor(None, myconstructor2)
+
+    data = yaml.load(input, Loader=Multi2)
+    if verbose:
+        print('Multi2:')
+        print(data)
+        print(native)
+    assert(data == native)
+
+
+test_multi_constructor.unittest = ['.multi', '.code']
+
+if __name__ == '__main__':
+    import test_appliance
+    test_appliance.run(globals())
+
diff --git a/tests/lib/test_yaml.py b/tests/lib/test_yaml.py
index e26342d61..352cd8d15 100644
--- a/tests/lib/test_yaml.py
+++ b/tests/lib/test_yaml.py
@@ -12,6 +12,7 @@
 from test_recursive import *
 from test_input_output import *
 from test_sort_keys import *
+from test_multi_constructor import *
 
 if __name__ == '__main__':
     import test_appliance
diff --git a/tests/lib/test_yaml_ext.py b/tests/lib/test_yaml_ext.py
index bdfda3e74..7f9357f66 100644
--- a/tests/lib/test_yaml_ext.py
+++ b/tests/lib/test_yaml_ext.py
@@ -1,6 +1,6 @@
 
 import _yaml, yaml
-import types, pprint
+import types, pprint, tempfile, sys, os
 
 yaml.PyBaseLoader = yaml.BaseLoader
 yaml.PySafeLoader = yaml.SafeLoader
@@ -233,6 +233,22 @@ def test_c_emitter(data_filename, canonical_filename, verbose=False):
 test_c_emitter.unittest = ['.data', '.canonical']
 test_c_emitter.skip = ['.skip-ext']
 
+def test_large_file(verbose=False):
+    SIZE_LINE = 24
+    SIZE_ITERATION = 0
+    SIZE_FILE = 31
+    if sys.maxsize <= 2**32:
+        return
+    if os.environ.get('PYYAML_TEST_GROUP', '') != 'all':
+        return
+    with tempfile.TemporaryFile() as temp_file:
+        for i in range(2**(SIZE_FILE-SIZE_ITERATION-SIZE_LINE) + 1):
+            temp_file.write(('-' + (' ' * (2**SIZE_LINE-4))+ '{}\n')*(2**SIZE_ITERATION))
+        temp_file.seek(0)
+        yaml.load(temp_file, Loader=yaml.CLoader)
+
+test_large_file.unittest = None
+
 def wrap_ext_function(function):
     def wrapper(*args, **kwds):
         _set_up()
diff --git a/tests/lib3/test_build.py b/tests/lib3/test_build.py
index 901e8ed6c..df3f943ba 100644
--- a/tests/lib3/test_build.py
+++ b/tests/lib3/test_build.py
@@ -2,7 +2,7 @@
 if __name__ == '__main__':
     import sys, os, distutils.util
     build_lib = 'build/lib'
-    build_lib_ext = os.path.join('build', 'lib.%s-%s' % (distutils.util.get_platform(), sys.version[0:3]))
+    build_lib_ext = os.path.join('build', 'lib.{}-{}.{}'.format(distutils.util.get_platform(), *sys.version_info))
     sys.path.insert(0, build_lib)
     sys.path.insert(0, build_lib_ext)
     import test_yaml, test_appliance
diff --git a/tests/lib3/test_build_ext.py b/tests/lib3/test_build_ext.py
index ff195d519..fa843f6e4 100644
--- a/tests/lib3/test_build_ext.py
+++ b/tests/lib3/test_build_ext.py
@@ -3,7 +3,7 @@
 if __name__ == '__main__':
     import sys, os, distutils.util
     build_lib = 'build/lib'
-    build_lib_ext = os.path.join('build', 'lib.%s-%s' % (distutils.util.get_platform(), sys.version[0:3]))
+    build_lib_ext = os.path.join('build', 'lib.{}-{}.{}'.format(distutils.util.get_platform(), *sys.version_info))
     sys.path.insert(0, build_lib)
     sys.path.insert(0, build_lib_ext)
     import test_yaml_ext, test_appliance
diff --git a/tests/lib3/test_constructor.py b/tests/lib3/test_constructor.py
index 427f53c30..877982db8 100644
--- a/tests/lib3/test_constructor.py
+++ b/tests/lib3/test_constructor.py
@@ -13,7 +13,7 @@ def execute(code):
 def _make_objects():
     global MyLoader, MyDumper, MyTestClass1, MyTestClass2, MyTestClass3, YAMLObject1, YAMLObject2,  \
             AnObject, AnInstance, AState, ACustomState, InitArgs, InitArgsWithState,    \
-            NewArgs, NewArgsWithState, Reduce, ReduceWithState, MyInt, MyList, MyDict,  \
+            NewArgs, NewArgsWithState, Reduce, ReduceWithState, Slots, MyInt, MyList, MyDict,  \
             FixedOffset, today, execute
 
     class MyLoader(yaml.Loader):
@@ -38,7 +38,18 @@ def construct1(constructor, node):
     def represent1(representer, native):
         return representer.represent_mapping("!tag1", native.__dict__)
 
+    def my_time_constructor(constructor, node):
+        seq = constructor.construct_sequence(node)
+        dt = seq[0]
+        tz = None
+        try:
+            tz = dt.tzinfo.tzname(dt)
+        except:
+            pass
+        return [dt, tz]
+
     yaml.add_constructor("!tag1", construct1, Loader=MyLoader)
+    yaml.add_constructor("!MyTime", my_time_constructor, Loader=MyLoader)
     yaml.add_representer(MyTestClass1, represent1, Dumper=MyDumper)
 
     class MyTestClass2(MyTestClass1, yaml.YAMLObject):
@@ -172,6 +183,17 @@ def __reduce__(self):
         def __setstate__(self, state):
             self.baz = state
 
+    class Slots:
+        __slots__ = ("foo", "bar", "baz")
+        def __init__(self, foo=None, bar=None, baz=None):
+            self.foo = foo
+            self.bar = bar
+            self.baz = baz
+
+        def __eq__(self, other):
+            return type(self) is type(other) and \
+                (self.foo, self.bar, self.baz) == (other.foo, other.bar, other.baz)
+
     class MyInt(int):
         def __eq__(self, other):
             return type(self) is type(other) and int(self) == int(other)
diff --git a/tests/lib3/test_multi_constructor.py b/tests/lib3/test_multi_constructor.py
new file mode 100644
index 000000000..f6e28fe0e
--- /dev/null
+++ b/tests/lib3/test_multi_constructor.py
@@ -0,0 +1,63 @@
+import yaml
+import pprint
+import sys
+
+def _load_code(expression):
+    return eval(expression)
+
+def myconstructor1(constructor, tag, node):
+    seq = constructor.construct_sequence(node)
+    return {tag: seq }
+
+def myconstructor2(constructor, tag, node):
+    seq = constructor.construct_sequence(node)
+    string = ''
+    try:
+        i = tag.index('!') + 1
+    except:
+        try:
+            i = tag.rindex(':') + 1
+        except:
+            pass
+    if i >= 0:
+        tag = tag[i:]
+    return { tag: seq }
+
+class Multi1(yaml.FullLoader):
+    pass
+class Multi2(yaml.FullLoader):
+    pass
+
+def test_multi_constructor(input_filename, code_filename, verbose=False):
+    input = open(input_filename, 'rb').read().decode('utf-8')
+    native = _load_code(open(code_filename, 'rb').read())
+
+    # default multi constructor for ! and !! tags
+    Multi1.add_multi_constructor('!', myconstructor1)
+    Multi1.add_multi_constructor('tag:yaml.org,2002:', myconstructor1)
+
+    data = yaml.load(input, Loader=Multi1)
+    if verbose:
+        print('Multi1:')
+        print(data)
+        print(native)
+    assert(data == native)
+
+
+    # default multi constructor for all tags
+    Multi2.add_multi_constructor(None, myconstructor2)
+
+    data = yaml.load(input, Loader=Multi2)
+    if verbose:
+        print('Multi2:')
+        print(data)
+        print(native)
+    assert(data == native)
+
+
+test_multi_constructor.unittest = ['.multi', '.code']
+
+if __name__ == '__main__':
+    import test_appliance
+    test_appliance.run(globals())
+
diff --git a/tests/lib3/test_yaml.py b/tests/lib3/test_yaml.py
index e26342d61..352cd8d15 100644
--- a/tests/lib3/test_yaml.py
+++ b/tests/lib3/test_yaml.py
@@ -12,6 +12,7 @@
 from test_recursive import *
 from test_input_output import *
 from test_sort_keys import *
+from test_multi_constructor import *
 
 if __name__ == '__main__':
     import test_appliance
diff --git a/tests/lib3/test_yaml_ext.py b/tests/lib3/test_yaml_ext.py
index 93d397b85..d902214ea 100644
--- a/tests/lib3/test_yaml_ext.py
+++ b/tests/lib3/test_yaml_ext.py
@@ -1,6 +1,6 @@
 
 import _yaml, yaml
-import types, pprint
+import types, pprint, tempfile, sys, os
 
 yaml.PyBaseLoader = yaml.BaseLoader
 yaml.PySafeLoader = yaml.SafeLoader
@@ -233,6 +233,22 @@ def test_c_emitter(data_filename, canonical_filename, verbose=False):
 test_c_emitter.unittest = ['.data', '.canonical']
 test_c_emitter.skip = ['.skip-ext']
 
+def test_large_file(verbose=False):
+    SIZE_LINE = 24
+    SIZE_ITERATION = 0
+    SIZE_FILE = 31
+    if sys.maxsize <= 2**32:
+        return
+    if os.environ.get('PYYAML_TEST_GROUP', '') != 'all':
+        return
+    with tempfile.TemporaryFile() as temp_file:
+        for i in range(2**(SIZE_FILE-SIZE_ITERATION-SIZE_LINE) + 1):
+            temp_file.write(bytes(('-' + (' ' * (2**SIZE_LINE-4))+ '{}\n')*(2**SIZE_ITERATION), 'utf-8'))
+        temp_file.seek(0)
+        yaml.load(temp_file, Loader=yaml.CLoader)
+
+test_large_file.unittest = None
+
 def wrap_ext_function(function):
     def wrapper(*args, **kwds):
         _set_up()
diff --git a/tox.ini b/tox.ini
index f0df1f688..867f1251b 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,8 +1,9 @@
 [tox]
-envlist = py27,pypy,py34,py35,py36,py37
+envlist = py27,pypy,py35,py36,py37,py38
 
 [testenv]
 deps =
     Cython
 commands =
     python setup.py test
+passenv = PYYAML_TEST_GROUP