diff -r 64bb01bce12c Lib/asyncio/locks.py
--- a/Lib/asyncio/locks.py	Sun Nov 30 20:39:04 2014 +0200
+++ b/Lib/asyncio/locks.py	Mon Dec 01 11:51:33 2014 +0900
@@ -307,7 +307,13 @@
                 self._waiters.remove(fut)
 
         finally:
-            yield from self.acquire()
+            # Must reacquire lock even if wait is cancelled
+            while True:
+                try:
+                    yield from self.acquire()
+                    break
+                except futures.CancelledError:
+                    pass
 
     @coroutine
     def wait_for(self, predicate):