diff --git a/unum/vendor/golang.org/x/net/internal/socket/sys_darwin.go b/unum/vendor/golang.org/x/net/internal/socket/sys_darwin.go
new file mode 100644
index 0000000..b17d223
--- /dev/null
+++ b/unum/vendor/golang.org/x/net/internal/socket/sys_darwin.go
@@ -0,0 +1,7 @@
+// Copyright 2017 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.
+
+package socket
+
+func probeProtocolStack() int { return 4 }