diff --git a/cmd/merge_zips/merge_zips.go b/cmd/merge_zips/merge_zips.go
index e16c00e..207b161 100644
--- a/cmd/merge_zips/merge_zips.go
+++ b/cmd/merge_zips/merge_zips.go
@@ -78,7 +78,7 @@
 	// parse args
 	flag.Parse()
 	args := flag.Args()
-	if len(args) < 2 {
+	if len(args) < 1 {
 		flag.Usage()
 		os.Exit(1)
 	}