--- a/netwerk/streamconv/converters/nsMultiMixedConv.cpp
+++ b/netwerk/streamconv/converters/nsMultiMixedConv.cpp
@@ -591,17 +591,17 @@ nsMultiMixedConv::OnDataAvailable(nsIReq
             rv = SendStart(channel);
             if (NS_FAILED(rv)) return rv;
         }
     }
 
     int32_t tokenLinefeed = 1;
     while ( (token = FindToken(cursor, bufLen)) ) {
 
-        if (((token + mTokenLen) < (cursor + bufLen)) &&
+        if (((token + mTokenLen + 1) < (cursor + bufLen)) &&
             (*(token + mTokenLen + 1) == '-')) {
             // This was the last delimiter so we can stop processing
             rv = SendData(cursor, LengthToToken(cursor, token));
             if (NS_FAILED(rv)) return rv;
             if (mPartChannel) {
                 mPartChannel->SetIsLastPart();
             }
             return SendStop(NS_OK);