diff --git a/Lib/asyncio/streams.py b/Lib/asyncio/streams.py
index a82cc79..dbb69d5 100644
--- a/Lib/asyncio/streams.py
+++ b/Lib/asyncio/streams.py
@@ -6,6 +6,7 @@ __all__ = ['StreamReader', 'StreamWriter', 'StreamReaderProtocol',
            'LimitOverrunError',
            ]
 
+import functools
 import socket
 
 if hasattr(socket, 'AF_UNIX'):
@@ -145,6 +146,15 @@ if hasattr(socket, 'AF_UNIX'):
         return (yield from loop.create_unix_server(factory, path, **kwds))
 
 
+def _copy_result(waiter, drain_waiter):
+    if drain_waiter.cancelled():
+        waiter.cancel()
+    elif drain_waiter.exception() is not None:
+        waiter.set_exception(drain_waiter.exception())
+    else:
+        waiter.set_result(drain_waiter.result())
+
+
 class FlowControlMixin(protocols.Protocol):
     """Reusable flow control logic for StreamWriter.drain().
 
@@ -204,10 +214,19 @@ class FlowControlMixin(protocols.Protocol):
             raise ConnectionResetError('Connection lost')
         if not self._paused:
             return
-        waiter = self._drain_waiter
-        assert waiter is None or waiter.cancelled()
+        drain_waiter = self._drain_waiter
+        if drain_waiter is None:
+            assert drain_waiter is None or drain_waiter.cancelled()
+            drain_waiter = self._loop.create_future()
+            self._drain_waiter = drain_waiter
+        else:
+            # FIXME: how should we handle cancellation here?
+            pass
+
         waiter = self._loop.create_future()
-        self._drain_waiter = waiter
+        cb = functools.partial(_copy_result, waiter)
+        drain_waiter.add_done_callback(cb)
+
         yield from waiter