diff --git a/hdr/debug.h b/hdr/debug.h
index d4cf7f1..70e6cf5 100644
--- a/hdr/debug.h
+++ b/hdr/debug.h
@@ -110,7 +110,7 @@
     defined(DEBUGFATDIR) || defined(DEBUGFATFS)
 #ifndef DEBUG_NEED_PRINTF
 #define DEBUG_NEED_PRINTF
-void printf(const char *, ...);
+VOID VA_CDECL printf(const char * fmt, ...);
 #endif
 #endif