diff --git a/expat/lib/xmlparse.c b/expat/lib/xmlparse.c
index 2de26ba2..40590e7f 100644
--- a/expat/lib/xmlparse.c
+++ b/expat/lib/xmlparse.c
@@ -1476,6 +1476,8 @@ XML_SetDoctypeDeclHandler(XML_Parser parser,
                           XML_StartDoctypeDeclHandler start,
                           XML_EndDoctypeDeclHandler end)
 {
+  if (parser == NULL)
+    return;
   startDoctypeDeclHandler = start;
   endDoctypeDeclHandler = end;
 }