diff --git a/src/objective-c/GRPCClient/GRPCCall.h b/src/objective-c/GRPCClient/GRPCCall.h
index 7a77ae60b6a99935395365bcfeb42c5f2755ad46..b9e741dfa8fe337357b7b34c623f98fa52887579 100644
--- a/src/objective-c/GRPCClient/GRPCCall.h
+++ b/src/objective-c/GRPCClient/GRPCCall.h
@@ -220,6 +220,8 @@ extern id const kGRPCTrailersKey;
  * messages to the response side of the call indefinitely (depending on the semantics of the
  * specific remote method called).
  * To finish a call right away, invoke cancel.
+ * host parameter should not contain the scheme (http:// or https://), only the name or IP addr
+ * and the port number, for example @"localhost:5050".
  */
 - (instancetype)initWithHost:(NSString *)host
                         path:(NSString *)path
diff --git a/src/objective-c/ProtoRPC/ProtoRPC.h b/src/objective-c/ProtoRPC/ProtoRPC.h
index f22d731f68b2740fe761a02d204d4bf337071ef2..5f91f6bce1e1496e71ad35aad6d2fc01dfac57f2 100644
--- a/src/objective-c/ProtoRPC/ProtoRPC.h
+++ b/src/objective-c/ProtoRPC/ProtoRPC.h
@@ -39,6 +39,10 @@
 __attribute__((deprecated("Please use GRPCProtoCall.")))
 @interface ProtoRPC : GRPCCall
 
+/**
+ * host parameter should not contain the scheme (http:// or https://), only the name or IP addr
+ * and the port number, for example @"localhost:5050".
+ */
 - (instancetype)initWithHost:(NSString *)host
                       method:(GRPCProtoMethod *)method
               requestsWriter:(GRXWriter *)requestsWriter