diff --git a/hex2chars.c b/hex2chars.c
--- a/hex2chars.c
+++ b/hex2chars.c
@@ -115,7 +115,7 @@
 
     if (argc != 2) {
         printf ("Usage: %s <string>\n", argv[0]);
-        exit (0);
+        return EXIT_FAILURE;
     }
 
     start = argv[1];