diff --git a/.travis.yml b/.travis.yml
index 5ff1d0035..60ad4719e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -16,7 +16,7 @@ install:
     # core dependencies
     - if [[ $RUN == nosetests ]]; then pip install pygments requests; fi
     # curtsies specific dependencies
-    - if [[ $RUN == nosetests ]]; then pip install 'curtsies >=0.1.15,<0.2.0' greenlet; fi
+    - if [[ $RUN == nosetests ]]; then pip install 'curtsies >=0.1.15,<0.2.0' greenlet watchdog; fi
     # translation specific dependencies
     - if [[ $RUN == nosetests ]]; then pip install babel; fi
     # documentation specific dependencies
diff --git a/bpython/curtsiesfrontend/filewatch.py b/bpython/curtsiesfrontend/filewatch.py
index 57955cbc5..6529f2e1b 100644
--- a/bpython/curtsiesfrontend/filewatch.py
+++ b/bpython/curtsiesfrontend/filewatch.py
@@ -19,8 +19,9 @@ def __init__(self, paths, on_change):
             self.observer = Observer()
             self.old_dirs = defaultdict(set)
             self.started = False
+            self.activated = False
             for path in paths:
-                self.add_module(path)
+                self._add_module(path)
 
         def reset(self):
             self.dirs = defaultdict(set)
@@ -28,8 +29,10 @@ def reset(self):
             self.old_dirs = defaultdict(set)
             self.observer.unschedule_all()
 
-        def add_module(self, path):
-            """Add a python module to track changes to"""
+        def _add_module(self, path):
+            """Add a python module to track changes to
+            
+            Can"""
             path = os.path.abspath(path)
             for suff in importcompletion.SUFFIXES:
                 if path.endswith(suff):
@@ -40,24 +43,36 @@ def add_module(self, path):
                 self.observer.schedule(self, dirname, recursive=False)
                 self.dirs[os.path.dirname(path)].add(path)
 
-        def add_module_later(self, path):
+        def _add_module_later(self, path):
             self.modules_to_add_later.append(path)
+            
+        def track_module(self, path):
+            """
+            Begins tracking this if activated, or remembers to track later.
+            """
+            if self.activated:
+                self._add_module(path)
+            else:
+                self._add_module_later(path)
 
         def activate(self):
+            if self.activated:
+                raise ValueError("%r is already activated." % (self,))
             if not self.started:
                 self.started = True
                 self.observer.start()
-            self.dirs = self.old_dirs
             for dirname in self.dirs:
                 self.observer.schedule(self, dirname, recursive=False)
             for module in self.modules_to_add_later:
-                self.add_module(module)
+                self._add_module(module)
             del self.modules_to_add_later[:]
+            self.activated = True
 
         def deactivate(self):
+            if not self.activated:
+                raise ValueError("%r is not activated." % (self,))
             self.observer.unschedule_all()
-            self.old_dirs = self.dirs
-            self.dirs = defaultdict(set)
+            self.activated = False
 
         def on_any_event(self, event):
             dirpath = os.path.dirname(event.src_path)
@@ -66,12 +81,5 @@ def on_any_event(self, event):
                 self.on_change(files_modified=[event.src_path])
 
 if __name__ == '__main__':
-    m = ModuleChangedEventHandler([])
-    m.add_module('./wdtest.py')
-    try:
-        while True:
-            time.sleep(1)
-    except KeyboardInterrupt:
-        m.observer.stop()
-    m.observer.join()
+    pass
 
diff --git a/bpython/curtsiesfrontend/repl.py b/bpython/curtsiesfrontend/repl.py
index 1d2b71fdc..3dd9fb0ad 100644
--- a/bpython/curtsiesfrontend/repl.py
+++ b/bpython/curtsiesfrontend/repl.py
@@ -366,18 +366,12 @@ def new_import(name, globals={}, locals={}, fromlist=[], level=-1):
                 except:
                     if name in old_module_locations:
                         loc = old_module_locations[name]
-                        if self.watching_files:
-                            self.watcher.add_module(loc)
-                        else:
-                            self.watcher.add_module_later(loc)
+                        self.watcher.track_module(loc)
                     raise
                 else:
                     if hasattr(m, "__file__"):
                         old_module_locations[name] = m.__file__
-                        if self.watching_files:
-                            self.watcher.add_module(m.__file__)
-                        else:
-                            self.watcher.add_module_later(m.__file__)
+                        self.watcher.track_module(m.__file__)
                 return m
             __builtins__['__import__'] = new_import
 
diff --git a/bpython/test/test_filewatch.py b/bpython/test/test_filewatch.py
new file mode 100644
index 000000000..242a5a153
--- /dev/null
+++ b/bpython/test/test_filewatch.py
@@ -0,0 +1,30 @@
+import mock
+import os
+
+try:
+    import unittest2 as unittest
+except ImportError:
+    import unittest
+
+from bpython.curtsiesfrontend.filewatch import ModuleChangedEventHandler
+
+class TestModuleChangeEventHandler(unittest.TestCase):
+    
+    def setUp(self):
+        self.module = ModuleChangedEventHandler([], 1)
+        self.module.observer = mock.Mock()
+        
+    def test_create_module_handler(self):
+        self.assertIsInstance(self.module, ModuleChangedEventHandler)
+        
+    def test_add_module(self):
+        self.module._add_module('something/test.py')
+        self.assertIn(os.path.abspath('something/test'), 
+                      self.module.dirs[os.path.abspath('something')])
+    
+    def test_activate_throws_error_when_already_activated(self):
+        self.module.activated = True
+        with self.assertRaises(ValueError):
+            self.module.activate()
+    
+    
\ No newline at end of file