diff --git a/mozilla/htmlparser/src/nsScanner.cpp b/mozilla/htmlparser/src/nsScanner.cpp
index c191f720b2b..3fb0e83d95d 100644
--- a/mozilla/htmlparser/src/nsScanner.cpp
+++ b/mozilla/htmlparser/src/nsScanner.cpp
@@ -555,7 +555,7 @@ nsresult nsScanner::Peek(nsAString& aStr, PRInt32 aNumChars, PRInt32 aOffset)
   }
   else {
     end = start;
-    end.advance(aNumChars + aOffset);
+    end.advance(aNumChars);
   }
 
   CopyUnicodeTo(start, end, aStr);