diff --git a/contrib/cmd/fs-idmap/fs-idmap.go b/contrib/cmd/fs-idmap/fs-idmap.go
index 45f171c69..5879c74e7 100644
--- a/contrib/cmd/fs-idmap/fs-idmap.go
+++ b/contrib/cmd/fs-idmap/fs-idmap.go
@@ -11,7 +11,7 @@ import (
 )
 
 func main() {
-	if len(os.Args) < 2 {
+	if len(os.Args) != 2 {
 		log.Fatalf("usage: %s path_to_mount_set_attr", os.Args[0])
 	}