diff --git a/src/kernel/Communicator.cc b/src/kernel/Communicator.cc
index 8e554b5117..1939b76fe6 100644
--- a/src/kernel/Communicator.cc
+++ b/src/kernel/Communicator.cc
@@ -1686,6 +1686,11 @@ int Communicator::sleep(SleepSession *session)
 	return -1;
 }
 
+int Communicator::is_handler_thread()
+{
+	return thrdpool_in_pool(this->thrdpool);
+}
+
 extern "C" void __thrdpool_schedule(const struct thrdpool_task *, void *,
 									thrdpool_t *);
 
diff --git a/src/kernel/Communicator.h b/src/kernel/Communicator.h
index e858d4a103..5a4e96d98d 100644
--- a/src/kernel/Communicator.h
+++ b/src/kernel/Communicator.h
@@ -27,10 +27,7 @@
 #include <pthread.h>
 #include <openssl/ssl.h>
 #include "list.h"
-#include "msgqueue.h"
-#include "thrdpool.h"
 #include "poller.h"
-#include "mpoller.h"
 
 class CommConnection
 {
@@ -263,13 +260,13 @@ class Communicator
 	void io_unbind(IOService *service);
 
 public:
+	int is_handler_thread();
 	int increase_handler_thread();
-	int is_handler_thread() { return thrdpool_in_pool(this->thrdpool); }
 
 private:
-	msgqueue_t *queue;
-	mpoller_t *mpoller;
-	thrdpool_t *thrdpool;
+	struct __mpoller *mpoller;
+	struct __msgqueue *queue;
+	struct __thrdpool *thrdpool;
 	int stop_flag;
 
 private:
diff --git a/src/kernel/Executor.h b/src/kernel/Executor.h
index 9181bf51dc..e43064190d 100644
--- a/src/kernel/Executor.h
+++ b/src/kernel/Executor.h
@@ -22,7 +22,6 @@
 #include <stddef.h>
 #include <pthread.h>
 #include "list.h"
-#include "thrdpool.h"
 
 class ExecQueue
 {
@@ -69,7 +68,7 @@ class Executor
 	int request(ExecSession *session, ExecQueue *queue);
 
 private:
-	thrdpool_t *thrdpool;
+	struct __thrdpool *thrdpool;
 
 private:
 	static void executor_thread_routine(void *context);
diff --git a/src/kernel/SleepRequest.h b/src/kernel/SleepRequest.h
index c625d96835..f2f1ed3010 100644
--- a/src/kernel/SleepRequest.h
+++ b/src/kernel/SleepRequest.h
@@ -20,6 +20,7 @@
 #define _SLEEPREQUEST_H_
 
 #include "SubTask.h"
+#include "Communicator.h"
 #include "CommScheduler.h"
 
 class SleepRequest : public SubTask, public SleepSession
diff --git a/src/kernel/thrdpool.c b/src/kernel/thrdpool.c
index 9419033211..6ec5b0e976 100644
--- a/src/kernel/thrdpool.c
+++ b/src/kernel/thrdpool.c
@@ -176,7 +176,7 @@ thrdpool_t *thrdpool_create(size_t nthreads, size_t stacksize)
 	thrdpool_t *pool;
 	int ret;
 
-	pool = (struct __thrdpool *)malloc(sizeof (struct __thrdpool));
+	pool = (thrdpool_t *)malloc(sizeof (thrdpool_t));
 	if (pool)
 	{
 		if (__thrdpool_init_locks(pool) >= 0)
diff --git a/src/kernel/thrdpool.h b/src/kernel/thrdpool.h
index ac8f722b92..71f4b2dc1c 100644
--- a/src/kernel/thrdpool.h
+++ b/src/kernel/thrdpool.h
@@ -41,8 +41,8 @@ extern "C"
  * A thread task can be scheduled by another task, which is very important,
  * even if the pool is being destroyed. Because thread task is hard to know
  * what's happening to the pool.
- * The thread pool can also be destroyed by a thread task. Although this seems
- * to be strange, it's very logical. Destroying thread pool in thread task
+ * The thread pool can also be destroyed by a thread task. This may sound
+ * strange, but it's very logical. Destroying thread pool in thread task
  * does not end the task thread. It'll run till the end of task.
  */