diff --git a/win/Qt/qt_pre.h b/win/Qt/qt_pre.h
index d3635e19b..b25c396b7 100644
--- a/win/Qt/qt_pre.h
+++ b/win/Qt/qt_pre.h
@@ -15,7 +15,7 @@
 #undef min
 #undef max
 
-#ifdef NO_C99
+#ifdef NOT_C99
 #ifdef NEED_INDEX
 #undef index
 #endif