1 files changed, 5 insertions, 2 deletions
diff --git a/include/grpc++/client_context.h b/include/grpc++/client_context.h
index 0cf6bdc647..a6e8ccc67c 100644
--- a/include/grpc++/client_context.h
+++ b/include/grpc++/client_context.h
@@ -35,8 +35,8 @@
 #define __GRPCPP_CLIENT_CONTEXT_H__
 
 #include <chrono>
+#include <map>
 #include <string>
-#include <vector>
 
 #include <grpc/support/log.h>
 #include <grpc/support/time.h>
@@ -49,6 +49,8 @@ struct grpc_completion_queue;
 
 namespace grpc {
 
+class CallOpBuffer;
+
 class ClientContext {
  public:
   ClientContext();
@@ -67,6 +69,7 @@ class ClientContext {
   ClientContext(const ClientContext &);
   ClientContext &operator=(const ClientContext &);
 
+  friend class CallOpBuffer;
   friend class Channel;
   friend class StreamContext;
 
@@ -84,7 +87,7 @@ class ClientContext {
   grpc_call *call_;
   grpc_completion_queue *cq_;
   gpr_timespec absolute_deadline_;
-  std::vector<std::pair<grpc::string, grpc::string> > metadata_;
+  std::multimap<grpc::string, grpc::string> metadata_;
 };
 
 }  // namespace grpc