diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/util/metautils/single_key.go b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/util/metautils/single_key.go
new file mode 100644
index 0000000..8a53871
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/util/metautils/single_key.go
@@ -0,0 +1,22 @@
+// Copyright 2016 Michal Witkowski. All Rights Reserved.
+// See LICENSE for licensing terms.
+
+package metautils
+
+import (
+	"encoding/base64"
+	"strings"
+)
+
+const (
+	binHdrSuffix = "-bin"
+)
+
+func encodeKeyValue(k, v string) (string, string) {
+	k = strings.ToLower(k)
+	if strings.HasSuffix(k, binHdrSuffix) {
+		val := base64.StdEncoding.EncodeToString([]byte(v))
+		v = string(val)
+	}
+	return k, v
+}