diff --git a/dlls/winecrt0/debug.c b/dlls/winecrt0/debug.c
index d7c170c429b..69a3ea7d59c 100644
--- a/dlls/winecrt0/debug.c
+++ b/dlls/winecrt0/debug.c
@@ -24,6 +24,7 @@
 #include "wine/port.h"
 
 #include <stdio.h>
+#include <stdarg.h>
 #include "windef.h"
 #include "winbase.h"
 #include "wine/debug.h"