diff --git a/unum/vendor/golang.org/x/sys/unix/dev_darwin.go b/unum/vendor/golang.org/x/sys/unix/dev_darwin.go
new file mode 100644
index 0000000..7d101d5
--- /dev/null
+++ b/unum/vendor/golang.org/x/sys/unix/dev_darwin.go
@@ -0,0 +1,24 @@
+// 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.
+
+// Functions to access/create device major and minor numbers matching the
+// encoding used in Darwin's sys/types.h header.
+
+package unix
+
+// Major returns the major component of a Darwin device number.
+func Major(dev uint64) uint32 {
+	return uint32((dev >> 24) & 0xff)
+}
+
+// Minor returns the minor component of a Darwin device number.
+func Minor(dev uint64) uint32 {
+	return uint32(dev & 0xffffff)
+}
+
+// Mkdev returns a Darwin device number generated from the given major and minor
+// components.
+func Mkdev(major, minor uint32) uint64 {
+	return uint64((major << 24) | minor)
+}