diff --git a/expat/lib/xmlparse.c b/expat/lib/xmlparse.c
index dfdb509b..991a5275 100644
--- a/expat/lib/xmlparse.c
+++ b/expat/lib/xmlparse.c
@@ -1647,6 +1647,12 @@ XML_SetHashSalt(XML_Parser parser,
 enum XML_Status XMLCALL
 XML_Parse(XML_Parser parser, const char *s, int len, int isFinal)
 {
+  if (parser == NULL)
+    return XML_STATUS_ERROR;
+  if (s == NULL && len != 0) {
+    errorCode = XML_ERROR_INVALID_ARGUMENT;
+    return XML_STATUS_ERROR;
+  }
   switch (ps_parsing) {
   case XML_SUSPENDED:
     errorCode = XML_ERROR_SUSPENDED;