diff --git a/layout/generic/nsTextTransformer.cpp b/layout/generic/nsTextTransformer.cpp
index f06fb93ad812..73f742035b56 100644
--- a/layout/generic/nsTextTransformer.cpp
+++ b/layout/generic/nsTextTransformer.cpp
@@ -859,7 +859,7 @@ nsTextTransformer::GetNextWord(PRBool aInWord,
   // beginning of the buffer
   if (aResetTransformBuf) {
     mBufferPos = 0;
-    SetTransformedTextIsAscii(LeaveAsAscii());
+    SetTransformedTextIsAscii(LeaveAsAscii() && !HasMultibyte());
   }
   prevBufferPos = mBufferPos;