diff --git a/vendor/google.golang.org/protobuf/internal/flags/proto_legacy_enable.go b/vendor/google.golang.org/protobuf/internal/flags/proto_legacy_enable.go
new file mode 100644
index 0000000..772e2f0
--- /dev/null
+++ b/vendor/google.golang.org/protobuf/internal/flags/proto_legacy_enable.go
@@ -0,0 +1,9 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build protolegacy
+
+package flags
+
+const protoLegacy = true