diff --git a/clients/fax500/rp500.c b/clients/fax500/rp500.c
index daee4ccd3e..67de48322d 100644
--- a/clients/fax500/rp500.c
+++ b/clients/fax500/rp500.c
@@ -12,6 +12,7 @@
 
 #include "portable.h"
 
+#include <stdio.h>
 #include <stdlib.h>
 
 #include <ac/ctype.h>