diff --git a/mozilla/content/base/src/nsXMLHttpRequest.cpp b/mozilla/content/base/src/nsXMLHttpRequest.cpp
index 634a5c03975..393fe95e8e0 100644
--- a/mozilla/content/base/src/nsXMLHttpRequest.cpp
+++ b/mozilla/content/base/src/nsXMLHttpRequest.cpp
@@ -1362,7 +1362,7 @@ nsXMLHttpRequest::StreamReaderFunc(nsIInputStream* in,
     nsCOMPtr<nsIInputStream> copyStream;
     rv = NS_NewByteInputStream(getter_AddRefs(copyStream), fromRawSegment, count);
 
-    if (NS_SUCCEEDED(rv)) {
+    if (NS_SUCCEEDED(rv) && xmlHttpRequest->mXMLParserStreamListener) {
       NS_ASSERTION(copyStream, "NS_NewByteInputStream lied");
       nsresult parsingResult = xmlHttpRequest->mXMLParserStreamListener
                                   ->OnDataAvailable(xmlHttpRequest->mReadRequest,