diff --git a/util/cpp/main.c b/util/cpp/main.c
index 4874c63d6..464de5cdb 100644
--- a/util/cpp/main.c
+++ b/util/cpp/main.c
@@ -59,6 +59,7 @@ compile(argc, argv)
 		WorkingDir = 0;
 		break;
 	default:
+		FileName = argv[0];
 		fatal("use: %s [options] [source]", prog_name);
 		break;
 	}