diff --git a/Lib/asyncio/base_events.py b/Lib/asyncio/base_events.py
index 60a189bdfb7ec9..c5c76b09c1f83c 100644
--- a/Lib/asyncio/base_events.py
+++ b/Lib/asyncio/base_events.py
@@ -141,6 +141,8 @@ def _ipaddr_info(host, port, family, type, proto):
     if '%' in host:
         # Linux's inet_pton doesn't accept an IPv6 zone index after host,
         # like '::1%lo0'.
+        # Such hosts should be resolved by getaddrinfo() to obtain the
+        # appropriate scope ID, and to have the zone part removed.
         return None
 
     for af in afs:
@@ -917,16 +919,16 @@ async def create_connection(
                     'host/port and sock can not be specified at the same time')
 
             infos = await self._ensure_resolved(
-                (host, port), family=family,
-                type=socket.SOCK_STREAM, proto=proto, flags=flags, loop=self)
+                host, port, family=family,
+                type=socket.SOCK_STREAM, proto=proto, flags=flags)
             if not infos:
                 raise OSError('getaddrinfo() returned empty list')
 
             if local_addr is not None:
                 laddr_infos = await self._ensure_resolved(
-                    local_addr, family=family,
+                    local_addr[0], local_addr[1], family=family,
                     type=socket.SOCK_STREAM, proto=proto,
-                    flags=flags, loop=self)
+                    flags=flags)
                 if not laddr_infos:
                     raise OSError('getaddrinfo() returned empty list')
 
@@ -1195,8 +1197,8 @@ async def create_datagram_endpoint(self, protocol_factory,
                             '2-tuple is expected')
 
                         infos = await self._ensure_resolved(
-                            addr, family=family, type=socket.SOCK_DGRAM,
-                            proto=proto, flags=flags, loop=self)
+                            *addr, family=family, type=socket.SOCK_DGRAM,
+                            proto=proto, flags=flags)
                         if not infos:
                             raise OSError('getaddrinfo() returned empty list')
 
@@ -1277,22 +1279,23 @@ async def create_datagram_endpoint(self, protocol_factory,
 
         return transport, protocol
 
-    async def _ensure_resolved(self, address, *,
+    async def _ensure_resolved(self, host, port, *,
                                family=0, type=socket.SOCK_STREAM,
-                               proto=0, flags=0, loop):
-        host, port = address[:2]
+                               proto=0, flags=0):
+        # Resolve (host, port) into a socket address tuple, skipping
+        # getaddrinfo() when possible.
         info = _ipaddr_info(host, port, family, type, proto)
         if info is not None:
             # "host" is already a resolved IP.
             return [info]
         else:
-            return await loop.getaddrinfo(host, port, family=family, type=type,
+            return await self.getaddrinfo(host, port, family=family, type=type,
                                           proto=proto, flags=flags)
 
     async def _create_server_getaddrinfo(self, host, port, family, flags):
-        infos = await self._ensure_resolved((host, port), family=family,
+        infos = await self._ensure_resolved(host, port, family=family,
                                             type=socket.SOCK_STREAM,
-                                            flags=flags, loop=self)
+                                            flags=flags)
         if not infos:
             raise OSError(f'getaddrinfo({host!r}) returned empty list')
         return infos
diff --git a/Lib/asyncio/selector_events.py b/Lib/asyncio/selector_events.py
index 112c4b15b8d8cf..e7e7dc9a0d9f85 100644
--- a/Lib/asyncio/selector_events.py
+++ b/Lib/asyncio/selector_events.py
@@ -458,16 +458,15 @@ def _sock_sendall(self, fut, sock, data):
     async def sock_connect(self, sock, address):
         """Connect to a remote socket at address.
 
+        `address` must be a socket address tuple(i.e. (ipv4_address, port) for
+        IPv4 or (ipv6_address, port, flowinfo, scopeid) for IPv6). It must
+        not be a (host, port) tuple that still needs to be resolved.
+
         This method is a coroutine.
         """
         if self._debug and sock.gettimeout() != 0:
             raise ValueError("the socket must be non-blocking")
 
-        if not hasattr(socket, 'AF_UNIX') or sock.family != socket.AF_UNIX:
-            resolved = await self._ensure_resolved(
-                address, family=sock.family, proto=sock.proto, loop=self)
-            _, _, _, _, address = resolved[0]
-
         fut = self.create_future()
         self._sock_connect(fut, sock, address)
         return await fut
diff --git a/Misc/NEWS.d/next/Library/2019-01-02-19-19-10.bpo-35545.lLbmO-.rst b/Misc/NEWS.d/next/Library/2019-01-02-19-19-10.bpo-35545.lLbmO-.rst
new file mode 100644
index 00000000000000..3094cccedb70ee
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-01-02-19-19-10.bpo-35545.lLbmO-.rst
@@ -0,0 +1,2 @@
+Fix mishandling of scoped IPv6 addresses in
+BaseEventLoop.create_connection().