diff -r 685ccab91706 Lib/weakref.py
--- a/Lib/weakref.py	Tue Oct 11 08:06:26 2016 +0200
+++ b/Lib/weakref.py	Thu Oct 13 21:23:15 2016 +0300
@@ -110,7 +110,7 @@ class WeakValueDictionary(collections.Mu
             if self is not None:
                 if self._iterating:
                     self._pending_removals.append(wr.key)
-                else:
+                elif self.data[wr.key]() is None:
                     del self.data[wr.key]
         self._remove = remove
         # A list of keys to be removed