diff --git a/src/server/mux.h b/src/server/mux.h
index d6dcb53e3a8884ed8349ae1da2ef28ee2ba6df16..99f5f2d901979f5f037b31ed70a18e5d11d359f6 100644
--- a/src/server/mux.h
+++ b/src/server/mux.h
@@ -1,5 +1,5 @@
 /*
- * $Id: mux.h,v 0.8 1995/01/01 20:17:23 ceder Exp $
+ * $Id: mux.h,v 0.9 1996/07/28 23:32:48 ceder Exp $
  * Copyright (C) 1991, 1993, 1994, 1995  Lysator Academic Computer Association.
  *
  * This file is part of the LysKOM server.
@@ -23,7 +23,7 @@
  * Please mail bug reports to bug-lyskom@lysator.liu.se. 
  */
 /*
- * $Id: mux.h,v 0.8 1995/01/01 20:17:23 ceder Exp $
+ * $Id: mux.h,v 0.9 1996/07/28 23:32:48 ceder Exp $
  *
 ** mux.h
 */
@@ -122,7 +122,11 @@ mux_write(Connection  	       * cp,
 extern int
 mux_printf(Connection  * cp,
 	   const char  * format,
-	   ...);
+	   ...)
+#  if HAVE_ATTRIBUTE_FORMAT_PRINTF
+    __attribute__ ((format (printf, 2, 3)))
+#  endif
+    ;
 #endif
 
 extern int