diff --git a/src/scheduler.c b/src/scheduler.c
index 3d730151..b35b2767 100644
--- a/src/scheduler.c
+++ b/src/scheduler.c
@@ -21,7 +21,7 @@
  */
 
 #include "xschem.h"
-
+#include <stdarg.h>
 /* n=1: messages in status bar
  * n=2: append str in ERC window messages
  * n=3: set ERC messages to str */