diff --git a/test/mbus_parse.c b/test/mbus_parse.c
index 2dfc32d..3f23999 100644
--- a/test/mbus_parse.c
+++ b/test/mbus_parse.c
@@ -31,7 +31,7 @@ main(int argc, char *argv[])
 
 	if (argc != 2)
     {
-        fprintf(stderr, "%s binary-file\n", argv[0]);
+        fprintf(stderr, "usage: %s binary-file\n", argv[0]);
         return 1;
     }
 
diff --git a/test/mbus_parse_hex.c b/test/mbus_parse_hex.c
index ced5a19..913b0d2 100644
--- a/test/mbus_parse_hex.c
+++ b/test/mbus_parse_hex.c
@@ -31,7 +31,7 @@ main(int argc, char *argv[])
 
 	if (argc != 2)
     {
-        fprintf(stderr, "%s binary-file\n", argv[0]);
+        fprintf(stderr, "usage: %s hex-file\n", argv[0]);
         return 1;
     }