diff -r 8f72bf88f471 Lib/asyncio/futures.py
--- a/Lib/asyncio/futures.py	Sat Feb 20 12:59:36 2016 -0800
+++ b/Lib/asyncio/futures.py	Sun Feb 21 11:48:11 2016 +1100
@@ -341,6 +341,8 @@
             raise InvalidStateError('{}: {!r}'.format(self._state, self))
         if isinstance(exception, type):
             exception = exception()
+        if isinstance(exception, StopIteration):
+            raise TypeError("Futures cannot raise StopIteration")
         self._exception = exception
         self._state = _FINISHED
         self._schedule_callbacks()