diff --git a/include/grpcpp/impl/server_builder_plugin.h b/include/grpcpp/impl/server_builder_plugin.h
index 9ab40bd7615..ccc8b832760 100644
--- a/include/grpcpp/impl/server_builder_plugin.h
+++ b/include/grpcpp/impl/server_builder_plugin.h
@@ -26,10 +26,10 @@
 namespace grpc_impl {
 
 class ChannelArguments;
-class ServerBuilder;
 class ServerInitializer;
 }  // namespace grpc_impl
 namespace grpc {
+class ServerBuilder;
 
 /// This interface is meant for internal usage only. Implementations of this
 /// interface should add themselves to a \a ServerBuilder instance through the
diff --git a/include/grpcpp/security/credentials.h b/include/grpcpp/security/credentials.h
index 43f68f3a9fa..8662b068a59 100644
--- a/include/grpcpp/security/credentials.h
+++ b/include/grpcpp/security/credentials.h
@@ -35,7 +35,6 @@ struct grpc_call;
 
 namespace grpc {
 class CallCredentials;
-class ChannelArguments;
 class ChannelCredentials;
 }  // namespace grpc
 namespace grpc_impl {
diff --git a/include/grpcpp/support/channel_arguments_impl.h b/include/grpcpp/support/channel_arguments_impl.h
index 1e1340e716d..8276c1d9099 100644
--- a/include/grpcpp/support/channel_arguments_impl.h
+++ b/include/grpcpp/support/channel_arguments_impl.h
@@ -24,6 +24,7 @@
 
 #include <grpc/compression.h>
 #include <grpc/grpc.h>
+#include <grpcpp/resource_quota.h>
 #include <grpcpp/support/config.h>
 
 namespace grpc {
@@ -31,7 +32,6 @@ namespace testing {
 class ChannelArgumentsTest;
 }  // namespace testing
 
-class ResourceQuota;
 class SecureChannelCredentials;
 }  // namespace grpc
 
diff --git a/src/cpp/client/create_channel.cc b/src/cpp/client/create_channel.cc
index 9426a4e7f6e..15bc193af72 100644
--- a/src/cpp/client/create_channel.cc
+++ b/src/cpp/client/create_channel.cc
@@ -25,10 +25,6 @@
 
 #include "src/cpp/client/create_channel_internal.h"
 
-namespace grpc {
-
-class ChannelArguments;
-}
 namespace grpc_impl {
 std::shared_ptr<grpc::Channel> CreateChannel(
     const grpc::string& target,