diff --git a/xpcom/io/nsBinaryStream.cpp b/xpcom/io/nsBinaryStream.cpp
index 5d2f077f1e16..976ebf6d4cdb 100644
--- a/xpcom/io/nsBinaryStream.cpp
+++ b/xpcom/io/nsBinaryStream.cpp
@@ -768,7 +768,13 @@ nsBinaryInputStream::ReadObject(PRBool aIsStrongRef, nsISupports* *aObject)
         { 0x7a22cc0, 0xce5, 0x11d3,
           { 0x93, 0x31, 0x0, 0x10, 0x4b, 0xa0, 0xfd, 0x40 }};
 
-    if (iid.Equals(oldURIiid)) {
+    // hackaround for bug 670542
+    static const nsIID oldURIiid2 =
+        { 0xd6d04c36, 0x0fa4, 0x4db3,
+          { 0xbe, 0x05, 0x4a, 0x18, 0x39, 0x71, 0x03, 0xe2 }};
+
+    if (iid.Equals(oldURIiid) ||
+        iid.Equals(oldURIiid2)) {
         const nsIID newURIiid = NS_IURI_IID;
         iid = newURIiid;
     }