diff --git a/modules/rostests/winetests/msvcrt/precomp.h b/modules/rostests/winetests/msvcrt/precomp.h
index 63a519d703c..8020f395b95 100644
--- a/modules/rostests/winetests/msvcrt/precomp.h
+++ b/modules/rostests/winetests/msvcrt/precomp.h
@@ -6,7 +6,9 @@
 #define _INC_WINDOWS
 #define COM_NO_WINDOWS_H
 
+#if !defined(_CRT_NON_CONFORMING_SWPRINTFS)
 #define _CRT_NON_CONFORMING_SWPRINTFS
+#endif
 
 #include <wine/test.h>