diff --git a/setup.c b/setup.c
index 860507e1fd..09c7932824 100644
--- a/setup.c
+++ b/setup.c
@@ -230,7 +230,7 @@ void verify_filename(const char *prefix,
 		     int diagnose_misspelt_rev)
 {
 	if (*arg == '-')
-		die("bad flag '%s' used after filename", arg);
+		die("option '%s' must come before non-option arguments", arg);
 	if (looks_like_pathspec(arg) || check_filename(prefix, arg))
 		return;
 	die_verify_filename(prefix, arg, diagnose_misspelt_rev);