diff -r c0224ff67cdd Lib/concurrent/futures/_base.py
--- a/Lib/concurrent/futures/_base.py	Mon Oct 13 10:39:41 2014 +0100
+++ b/Lib/concurrent/futures/_base.py	Mon Oct 13 16:45:00 2014 +0100
@@ -332,9 +332,7 @@
                 return True
 
             self._state = CANCELLED
-            self._condition.notify_all()
 
-        self._invoke_callbacks()
         return True
 
     def cancelled(self):
@@ -468,9 +466,7 @@
                 self._state = CANCELLED_AND_NOTIFIED
                 for waiter in self._waiters:
                     waiter.add_cancelled(self)
-                # self._condition.notify_all() is not necessary because
-                # self.cancel() triggers a notification.
-                return False
+                self._condition.notify_all()
             elif self._state == PENDING:
                 self._state = RUNNING
                 return True
@@ -480,6 +476,10 @@
                                 self._state)
                 raise RuntimeError('Future in unexpected state')
 
+        # fall through if state was CANCELLED
+        self._invoke_callbacks()
+        return False
+
     def set_result(self, result):
         """Sets the return value of work associated with the future.
 
diff -r c0224ff67cdd Lib/test/test_concurrent_futures.py
--- a/Lib/test/test_concurrent_futures.py	Mon Oct 13 10:39:41 2014 +0100
+++ b/Lib/test/test_concurrent_futures.py	Mon Oct 13 16:45:00 2014 +0100
@@ -513,6 +513,7 @@
         f = Future()
         f.add_done_callback(fn)
         self.assertTrue(f.cancel())
+        f.set_running_or_notify_cancel()
         self.assertTrue(was_cancelled)
 
     def test_done_callback_raises(self):