diff --git a/cmd/stackprot_test.c b/cmd/stackprot_test.c
index 1e26193..f347028 100644
--- a/cmd/stackprot_test.c
+++ b/cmd/stackprot_test.c
@@ -17,7 +17,8 @@
 
 	memset(a, 0xa5, 512);
 
-	printf("We have smashed our stack as this should not exceed 128: sizeof(a) = %ld\n", strlen(a));
+	printf("We have smashed our stack as this should not exceed 128: sizeof(a) = %zd\n",
+	       strlen(a));
 
 	return 0;
 }