diff --git a/examples/mifare-classic-format.c b/examples/mifare-classic-format.c
index 498ccdb..70152e6 100644
--- a/examples/mifare-classic-format.c
+++ b/examples/mifare-classic-format.c
@@ -57,7 +57,7 @@ struct {
     .interactive = true
 };
 
-void
+static void
 display_progress (void)
 {
     at_block++;