diff --git a/UTILITIES/x11idle.c b/UTILITIES/x11idle.c
index 5299d3bd4..22cefe1e6 100644
--- a/UTILITIES/x11idle.c
+++ b/UTILITIES/x11idle.c
@@ -23,6 +23,6 @@ main() {
     }
 
     //info was retrieved successfully, print idle time
-    printf("%u\n", info->idle);
+    printf("%lu\n", info->idle);
     return 0;
 }