return NULL on error
diff --git a/Modules/pyexpat.c b/Modules/pyexpat.c
index 7c610a8..4e806e2 100644
--- a/Modules/pyexpat.c
+++ b/Modules/pyexpat.c
@@ -1805,7 +1805,7 @@
 
     version = PyUnicode_FromString(PY_VERSION);
     if (!version)
-        return;
+        return NULL;
     PyModule_AddObject(m, "__version__", version);
     PyModule_AddStringConstant(m, "EXPAT_VERSION",
                                (char *) XML_ExpatVersion());