Include the weakref object interface.
diff --git a/Include/Python.h b/Include/Python.h
index 9757a70..c0eed94 100644
--- a/Include/Python.h
+++ b/Include/Python.h
@@ -90,6 +90,7 @@
 #include "cellobject.h"
 #include "iterobject.h"
 #include "descrobject.h"
+#include "weakrefobject.h"
 
 #include "codecs.h"
 #include "pyerrors.h"