diff --git a/src/objective-c/ProtoRPC/ProtoRPC.m b/src/objective-c/ProtoRPC/ProtoRPC.m
index 48a38bd35ac..03e6839c5a0 100644
--- a/src/objective-c/ProtoRPC/ProtoRPC.m
+++ b/src/objective-c/ProtoRPC/ProtoRPC.m
@@ -175,7 +175,7 @@ static NSError *ErrorForBadProto(id proto, Class expectedClass, NSError *parsing
 }
 
 - (void)writeMessage:(GPBMessage *)message {
-  NSAssert([message isKindOfClass:[GPBMessage class]]);
+  NSAssert([message isKindOfClass:[GPBMessage class]], @"Parameter message must be a GPBMessage");
   if (![message isKindOfClass:[GPBMessage class]]) {
     NSLog(@"Failed to send a message that is non-proto.");
     return;
@@ -199,7 +199,7 @@ static NSError *ErrorForBadProto(id proto, Class expectedClass, NSError *parsing
 
 - (void)didReceiveInitialMetadata:(NSDictionary *)initialMetadata {
   @synchronized(self) {
-    if (initialMetadata != nil && [_handler respondsToSelector:@selector(initialMetadata:)]) {
+    if (initialMetadata != nil && [_handler respondsToSelector:@selector(didReceiveInitialMetadata:)]) {
       dispatch_async(_dispatchQueue, ^{
         id<GRPCProtoResponseHandler> copiedHandler = nil;
         @synchronized(self) {