diff --git a/src/objective-c/GRPCClient/GRPCCall.h b/src/objective-c/GRPCClient/GRPCCall.h
index 985743433cf..6d8b9c1b127 100644
--- a/src/objective-c/GRPCClient/GRPCCall.h
+++ b/src/objective-c/GRPCClient/GRPCCall.h
@@ -153,6 +153,14 @@ extern NSString *const kGRPCTrailersKey;
 /** An object can implement this protocol to receive responses from server from a call. */
 @protocol GRPCResponseHandler<NSObject>
 
+@required
+
+/**
+ * All the responses must be issued to a user-provided dispatch queue. This property specifies the
+ * dispatch queue to be used for issuing the notifications.
+ */
+@property(atomic, readonly) dispatch_queue_t dispatchQueue;
+
 @optional
 
 /**
@@ -175,14 +183,6 @@ extern NSString *const kGRPCTrailersKey;
 - (void)didCloseWithTrailingMetadata:(nullable NSDictionary *)trailingMetadata
                              error:(nullable NSError *)error;
 
-@required
-
-/**
- * All the responses must be issued to a user-provided dispatch queue. This property specifies the
- * dispatch queue to be used for issuing the notifications.
- */
-@property(atomic, readonly) dispatch_queue_t dispatchQueue;
-
 @end
 
 /**
diff --git a/src/objective-c/GRPCClient/GRPCCall.m b/src/objective-c/GRPCClient/GRPCCall.m
index 48253677bd3..e75ca7193a7 100644
--- a/src/objective-c/GRPCClient/GRPCCall.m
+++ b/src/objective-c/GRPCClient/GRPCCall.m
@@ -856,9 +856,7 @@ const char *kCFStreamVarName = "grpc_cfstream";
   _retainSelf = self;
 
   if (_callOptions == nil) {
-    GRPCMutableCallOptions *callOptions;
-
-    callOptions = [[GRPCHost callOptionsForHost:_host] mutableCopy];
+    GRPCMutableCallOptions *callOptions = [[GRPCHost callOptionsForHost:_host] mutableCopy];
     if (_serverName.length != 0) {
       callOptions.serverAuthority = _serverName;
     }
diff --git a/src/objective-c/GRPCClient/private/GRPCChannelPool+Test.h b/src/objective-c/GRPCClient/private/GRPCChannelPool+Test.h
new file mode 100644
index 00000000000..4e7c988585d
--- /dev/null
+++ b/src/objective-c/GRPCClient/private/GRPCChannelPool+Test.h
@@ -0,0 +1,49 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#import "GRPCChannelPool.h"
+
+/** Test-only interface for \a GRPCPooledChannel. */
+@interface GRPCPooledChannel (Test)
+
+/**
+ * Initialize a pooled channel with non-default destroy delay for testing purpose.
+ */
+- (nullable instancetype)initWithChannelConfiguration:
+(GRPCChannelConfiguration *)channelConfiguration
+                                         destroyDelay:(NSTimeInterval)destroyDelay;
+
+/**
+ * Return the pointer to the raw channel wrapped.
+ */
+@property(atomic, readonly) GRPCChannel *wrappedChannel;
+
+@end
+
+/** Test-only interface for \a GRPCChannelPool. */
+@interface GRPCChannelPool (Test)
+
+/**
+ * Get an instance of pool isolated from the global shared pool with channels' destroy delay being
+ * \a destroyDelay.
+ */
+- (nullable instancetype)initTestPool;
+
+@end
+
+
diff --git a/src/objective-c/GRPCClient/private/GRPCChannelPool.h b/src/objective-c/GRPCClient/private/GRPCChannelPool.h
index 7c6f2b3bbfa..d1f28ec9bfa 100644
--- a/src/objective-c/GRPCClient/private/GRPCChannelPool.h
+++ b/src/objective-c/GRPCClient/private/GRPCChannelPool.h
@@ -75,23 +75,6 @@ NS_ASSUME_NONNULL_BEGIN
 
 @end
 
-/** Test-only interface for \a GRPCPooledChannel. */
-@interface GRPCPooledChannel (Test)
-
-/**
- * Initialize a pooled channel with non-default destroy delay for testing purpose.
- */
-- (nullable instancetype)initWithChannelConfiguration:
-(GRPCChannelConfiguration *)channelConfiguration
-                                         destroyDelay:(NSTimeInterval)destroyDelay;
-
-/**
- * Return the pointer to the raw channel wrapped.
- */
-@property(atomic, readonly) GRPCChannel *wrappedChannel;
-
-@end
-
 /**
  * Manage the pool of connected channels. When a channel is no longer referenced by any call,
  * destroy the channel after a certain period of time elapsed.
@@ -119,15 +102,4 @@ NS_ASSUME_NONNULL_BEGIN
 
 @end
 
-/** Test-only interface for \a GRPCChannelPool. */
-@interface GRPCChannelPool (Test)
-
-/**
- * Get an instance of pool isolated from the global shared pool with channels' destroy delay being
- * \a destroyDelay.
- */
-- (nullable instancetype)initTestPool;
-
-@end
-
 NS_ASSUME_NONNULL_END
diff --git a/src/objective-c/GRPCClient/private/GRPCChannelPool.m b/src/objective-c/GRPCClient/private/GRPCChannelPool.m
index 391022efd19..349bdd44a65 100644
--- a/src/objective-c/GRPCClient/private/GRPCChannelPool.m
+++ b/src/objective-c/GRPCClient/private/GRPCChannelPool.m
@@ -22,6 +22,7 @@
 #import "GRPCChannel.h"
 #import "GRPCChannelFactory.h"
 #import "GRPCChannelPool.h"
+#import "GRPCChannelPool+Test.h"
 #import "GRPCConnectivityMonitor.h"
 #import "GRPCCronetChannelFactory.h"
 #import "GRPCInsecureChannelFactory.h"
@@ -59,9 +60,7 @@ static const NSTimeInterval kDefaultChannelDestroyDelay = 30;
 - (void)dealloc {
   // Disconnect GRPCWrappedCall objects created but not yet removed
   if (_wrappedCalls.allObjects.count != 0) {
-    NSEnumerator *enumerator = [_wrappedCalls objectEnumerator];
-    GRPCWrappedCall *wrappedCall;
-    while ((wrappedCall = [enumerator nextObject])) {
+    for (GRPCWrappedCall *wrappedCall in _wrappedCalls.allObjects) {
       [wrappedCall channelDisconnected];
     };
   }
@@ -73,7 +72,7 @@ callOptions:(GRPCCallOptions *)callOptions {
   NSAssert(path.length > 0, @"path must not be empty.");
   NSAssert(queue != nil, @"completionQueue must not be empty.");
   NSAssert(callOptions, @"callOptions must not be empty.");
-  if (path.length == 0 || queue == nil || callOptions == nil) return NULL;
+  if (path.length == 0 || queue == nil || callOptions == nil) return nil;
 
   GRPCWrappedCall *call = nil;
 
diff --git a/src/objective-c/ProtoRPC/ProtoRPC.h b/src/objective-c/ProtoRPC/ProtoRPC.h
index 287aa0369b1..2e0400a323f 100644
--- a/src/objective-c/ProtoRPC/ProtoRPC.h
+++ b/src/objective-c/ProtoRPC/ProtoRPC.h
@@ -28,6 +28,14 @@ NS_ASSUME_NONNULL_BEGIN
 /** An object can implement this protocol to receive responses from server from a call. */
 @protocol GRPCProtoResponseHandler<NSObject>
 
+@required
+
+/**
+ * All the responses must be issued to a user-provided dispatch queue. This property specifies the
+ * dispatch queue to be used for issuing the notifications.
+ */
+@property(atomic, readonly) dispatch_queue_t dispatchQueue;
+
 @optional
 
 /**
@@ -49,14 +57,6 @@ NS_ASSUME_NONNULL_BEGIN
 - (void)didCloseWithTrailingMetadata:(nullable NSDictionary *)trailingMetadata
                                error:(nullable NSError *)error;
 
-@required
-
-/**
- * All the responses must be issued to a user-provided dispatch queue. This property specifies the
- * dispatch queue to be used for issuing the notifications.
- */
-@property(atomic, readonly) dispatch_queue_t dispatchQueue;
-
 @end
 
 /** A unary-request RPC call with Protobuf. */
diff --git a/src/objective-c/ProtoRPC/ProtoRPC.m b/src/objective-c/ProtoRPC/ProtoRPC.m
index 886e31ce58a..0f63f72f536 100644
--- a/src/objective-c/ProtoRPC/ProtoRPC.m
+++ b/src/objective-c/ProtoRPC/ProtoRPC.m
@@ -75,7 +75,6 @@ static NSError *ErrorForBadProto(id proto, Class expectedClass, NSError *parsing
 
 - (void)cancel {
   [_call cancel];
-  _call = nil;
 }
 
 @end
@@ -124,7 +123,7 @@ static NSError *ErrorForBadProto(id proto, Class expectedClass, NSError *parsing
 #else
     {
 #endif
-      _dispatchQueue = dispatch_queue_create(nil, DISPATCH_QUEUE_SERIAL);
+      _dispatchQueue = dispatch_queue_create(NULL, DISPATCH_QUEUE_SERIAL);
     }
     dispatch_set_target_queue(_dispatchQueue, handler.dispatchQueue);
 
@@ -145,7 +144,7 @@ static NSError *ErrorForBadProto(id proto, Class expectedClass, NSError *parsing
     copiedCall = _call;
     _call = nil;
     if ([_handler respondsToSelector:@selector(didCloseWithTrailingMetadata:error:)]) {
-      dispatch_async(_handler.dispatchQueue, ^{
+      dispatch_async(_dispatchQueue, ^{
         id<GRPCProtoResponseHandler> copiedHandler = nil;
         @synchronized(self) {
           copiedHandler = self->_handler;
diff --git a/src/objective-c/tests/ChannelTests/ChannelPoolTest.m b/src/objective-c/tests/ChannelTests/ChannelPoolTest.m
index dc42d7c341d..eab8c5193fb 100644
--- a/src/objective-c/tests/ChannelTests/ChannelPoolTest.m
+++ b/src/objective-c/tests/ChannelTests/ChannelPoolTest.m
@@ -19,7 +19,7 @@
 #import <XCTest/XCTest.h>
 
 #import "../../GRPCClient/private/GRPCChannel.h"
-#import "../../GRPCClient/private/GRPCChannelPool.h"
+#import "../../GRPCClient/private/GRPCChannelPool+Test.h"
 #import "../../GRPCClient/private/GRPCCompletionQueue.h"
 
 #define TEST_TIMEOUT 32
diff --git a/src/objective-c/tests/ChannelTests/ChannelTests.m b/src/objective-c/tests/ChannelTests/ChannelTests.m
index ee7f8b6fddb..7c80868c2c9 100644
--- a/src/objective-c/tests/ChannelTests/ChannelTests.m
+++ b/src/objective-c/tests/ChannelTests/ChannelTests.m
@@ -21,6 +21,7 @@
 #import "../../GRPCClient/GRPCCallOptions.h"
 #import "../../GRPCClient/private/GRPCChannel.h"
 #import "../../GRPCClient/private/GRPCChannelPool.h"
+#import "../../GRPCClient/private/GRPCChannelPool+Test.h"
 #import "../../GRPCClient/private/GRPCCompletionQueue.h"
 #import "../../GRPCClient/private/GRPCWrappedCall.h"