diff --git a/volume/local/local_unix.go b/volume/local/local_unix.go
index c8163ccd13..4a3ee02c7e 100644
--- a/volume/local/local_unix.go
+++ b/volume/local/local_unix.go
@@ -32,9 +32,9 @@ var (
 		"size":   {}, // quota size limit
 	}
 	mandatoryOpts = map[string][]string{
-		"device": []string{"type"},
-		"type":   []string{"device"},
-		"o":      []string{"device", "type"},
+		"device": {"type"},
+		"type":   {"device"},
+		"o":      {"device", "type"},
 	}
 )