diff --git a/src/core/piincludes_p.h b/src/core/piincludes_p.h
index 95afe455..4a2d808c 100644
--- a/src/core/piincludes_p.h
+++ b/src/core/piincludes_p.h
@@ -22,6 +22,7 @@
 
 #include "pibase.h"
 #ifdef WINDOWS
+#  include <stdarg.h>
 #  include <windef.h>
 #  include <winbase.h>
 typedef void(*PINtSetTimerResolution)(ULONG, BOOLEAN, PULONG);