diff --git a/widget/src/windows/nsWindow.h b/widget/src/windows/nsWindow.h
index 55657f00cb50..43a0a2bdd79e 100644
--- a/widget/src/windows/nsWindow.h
+++ b/widget/src/windows/nsWindow.h
@@ -36,7 +36,7 @@
 #include "nsVoidArray.h"
 
 //#define DRAG_DROP
-#if DRAG_DROP
+#ifdef DRAG_DROP
 class CfDropTarget;
 class CfDropSource;
 class CfDragDrop;