diff --git a/widget/cocoa/TextInputHandler.h b/widget/cocoa/TextInputHandler.h
index 7d457b42642..faa2768ba05 100644
--- a/widget/cocoa/TextInputHandler.h
+++ b/widget/cocoa/TextInputHandler.h
@@ -887,9 +887,6 @@ protected:
 private:
   // If mIsIMEComposing is true, the composition string is stored here.
   NSString* mIMECompositionString;
-  // mLastDispatchedCompositionString stores the lastest dispatched composition
-  // string by compositionupdate event.
-  nsString mLastDispatchedCompositionString;
 
   NSRange mMarkedRange;
   NSRange mSelectedRange;