diff --git a/Makefile b/Makefile
index 448c196..742457c 100644
--- a/Makefile
+++ b/Makefile
@@ -32,3 +32,4 @@ install: ## build blackbean.
 
 clean: ## Remove test report.
 	@rm -f *.out
+
diff --git a/cmd/snapshot.go b/cmd/snapshot.go
index e2367ee..de7861d 100644
--- a/cmd/snapshot.go
+++ b/cmd/snapshot.go
@@ -155,7 +155,7 @@ func restoreSnapshot(cli *elasticsearch.Client, out io.Writer) *cobra.Command {
 		}
 	)
 	f := command.Flags()
-	f.StringVar(&snapshots, "snapshot", "_all", "to get specific snapshot")
+	f.StringVar(&snapshots, "snapshot", "", "to get specific snapshot")
 	err := command.RegisterFlagCompletionFunc("snapshot", func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
 		if len(args) == 1 {
 			return so.getRepoAllSnapshotsForFlag(args[0]), cobra.ShellCompDirectiveNoFileComp
@@ -171,6 +171,7 @@ func restoreSnapshot(cli *elasticsearch.Client, out io.Writer) *cobra.Command {
 	_ = command.MarkFlagRequired("index")
 	_ = command.MarkFlagRequired("rename_pattern")
 	_ = command.MarkFlagRequired("rename_replacement")
+	_ = command.MarkFlagRequired("snapshot")
 	return command
 }
 
diff --git a/pkg/util/decoder.go b/pkg/util/decoder.go
index 8ec6a01..0f98750 100644
--- a/pkg/util/decoder.go
+++ b/pkg/util/decoder.go
@@ -59,17 +59,6 @@ func Unmarshal(data []byte, v interface{}) error {
 	}
 }
 
-//// ToJSON converts a single YAML document into a JSON document
-//// or returns an error. If the document appears to be JSON the
-//// YAML decoding path is not used (so that error messages are
-//// JSON specific).
-//func ToJSON(data []byte) ([]byte, error) {
-//	if hasJSONPrefix(data) {
-//		return data, nil
-//	}
-//	return yaml.YAMLToJSON(data)
-//}
-
 // YAMLToJSONDecoder decodes YAML documents from an io.Reader by
 // separating individual documents. It first converts the YAML
 // body to JSON, then unmarshals the JSON.