diff -r a7b498c16f9e Python/getargs.c
--- a/Python/getargs.c	Sun Dec 16 17:25:05 2012 +0000
+++ b/Python/getargs.c	Wed Dec 19 22:36:53 2012 +0000
@@ -572,6 +572,15 @@
     char c = *format++;
     char *sarg;
 
+	if (PyWeakref_CheckProxy(arg)) {
+		arg = PyWeakref_GET_OBJECT(arg);
+		if (arg == Py_None) {
+			PyErr_SetString(PyExc_ReferenceError,
+							"weakly-referenced object no longer exists");
+			return NULL;
+		}
+    }
+
     switch (c) {
 
     case 'b': { /* unsigned byte -- very short int */