Index: Modules/timemodule.c
===================================================================
--- Modules/timemodule.c	(revision 78430)
+++ Modules/timemodule.c	(working copy)
@@ -566,6 +566,10 @@
 	} else if (!gettmarg(tup, &buf))
 		return NULL;
 	p = asctime(&buf);
+	if (p == NULL) {
+	        PyErr_SetString(PyExc_ValueError, "invalid time");
+		return NULL;
+	}
 	if (p[24] == '\n')
 		p[24] = '\0';
 	return PyString_FromString(p);