diff --git a/base-hw/include/base/native_types.h b/base-hw/include/base/native_types.h
index c868f7e5b3..2fcb3d701a 100644
--- a/base-hw/include/base/native_types.h
+++ b/base-hw/include/base/native_types.h
@@ -47,31 +47,10 @@ namespace Genode
 	 */
 	inline Native_thread_id thread_invalid_id() { return 0; }
 
-	/**
-	 * Message that is communicated synchronously
-	 */
-	struct Msg
-	{
-		/**
-		 * Types of synchronously communicated messages
-		 */
-		struct Type
-		{
-			enum Id {
-				INVALID = 0,
-				STARTUP = 1,
-				IPC     = 2,
-			};
-		};
-
-		Type::Id type;
-		uint8_t  data[];
-	};
-
 	/**
 	 * Message that is communicated between user threads
 	 */
-	struct Ipc_msg : Msg
+	struct Ipc_msg
 	{
 		size_t  size;
 		uint8_t data[];
@@ -136,7 +115,7 @@ namespace Genode
 	struct Native_pd_args { };
 }
 
-class Genode::Startup_msg : public Msg
+class Genode::Startup_msg
 {
 	private:
 
@@ -149,34 +128,26 @@ class Genode::Startup_msg : public Msg
 		 *
 		 * \param thread_id  kernel name of the thread that is started
 		 */
-		void init(Native_thread_id const thread_id)
-		{
-			_thread_id = thread_id;
-			type = Msg::Type::STARTUP;
-		}
+		void init(Native_thread_id const thread_id) { _thread_id = thread_id; }
 
-		/**
-		 * Return kernel name of started thread message-type-save
-		 */
-		Native_thread_id thread_id() const
-		{
-			if (type == Msg::Type::STARTUP) { return _thread_id; }
-			return thread_invalid_id();
-		}
+
+		/***************
+		 ** Accessors **
+		 ***************/
+
+		Native_thread_id thread_id() const { return _thread_id; }
 };
 
 struct Genode::Native_utcb
 {
 	union {
 		uint8_t     data[1 << MIN_MAPPING_SIZE_LOG2];
-		Msg         msg;
 		Ipc_msg     ipc_msg;
 		Startup_msg startup_msg;
 	};
 
 	void call_await_request_msg(void * & buf_base, size_t & buf_size)
 	{
-		msg.type = Msg::Type::INVALID;
 		buf_base = base();
 		buf_size = size();
 	}
@@ -184,7 +155,6 @@ struct Genode::Native_utcb
 	void call_send_request_msg(void * & msg_base, size_t & msg_size,
 	                           void * & buf_base, size_t & buf_size)
 	{
-		msg.type = Msg::Type::IPC;
 		msg_base = ipc_msg_base();
 		msg_size = ipc_msg_size();
 		buf_base = base();
@@ -193,7 +163,6 @@ struct Genode::Native_utcb
 
 	void call_send_reply_msg(void * & msg_base, size_t & msg_size)
 	{
-		msg.type = Msg::Type::IPC;
 		msg_base = ipc_msg_base();
 		msg_size = ipc_msg_size();
 	}
diff --git a/base-hw/include/kernel/interface.h b/base-hw/include/kernel/interface.h
index 3ba1991c41..7894c31e85 100644
--- a/base-hw/include/kernel/interface.h
+++ b/base-hw/include/kernel/interface.h
@@ -315,42 +315,51 @@ namespace Kernel
 
 
 	/**
-	 * Send IPC request and await corresponding IPC reply
+	 * Send request message and await receipt of corresponding reply message
 	 *
 	 * \param thread_id  kernel name of targeted thread
 	 *
-	 * As soon as call returns, callers UTCB provides received message.
+	 * \retval  0  succeeded
+	 * \retval -1  failed
+	 *
+	 * If the call returns successful, the received message is located at the
+	 * base of the callers userland thread-context.
 	 */
-	inline void send_request_msg(unsigned const thread_id)
+	inline int send_request_msg(unsigned const thread_id)
 	{
-		call(Call_id::SEND_REQUEST_MSG, thread_id);
+		return call(Call_id::SEND_REQUEST_MSG, thread_id);
 	}
 
 
 	/**
-	 * Await the receipt of a message
+	 * Await receipt of request message
 	 *
-	 * \return  type of received message
+	 * \retval  0  succeeded
+	 * \retval -1  failed
 	 *
-	 * As soon as call returns, callers UTCB provides received message.
+	 * If the call returns successful, the received message is located at the
+	 * base of the callers userland thread-context.
 	 */
-	inline void await_request_msg()
+	inline int await_request_msg()
 	{
-		call(Call_id::AWAIT_REQUEST_MSG);
+		return call(Call_id::AWAIT_REQUEST_MSG);
 	}
 
 
 	/**
-	 * Reply to lastly received message
+	 * Reply to lastly received request message
 	 *
 	 * \param await_request_msg  wether the call shall await a request message
 	 *
-	 * As soon as call returns, callers UTCB provides received message if
-	 * await_request_msg is set.
+	 * \retval  0  await_request_msg == 0 or request-message receipt succeeded
+	 * \retval -1  await_request_msg == 1 and request-message receipt failed
+	 *
+	 * If the call returns successful and await_request_msg == 1, the received
+	 * message is located at the base of the callers userland thread-context.
 	 */
-	inline void send_reply_msg(bool const await_request_msg)
+	inline int send_reply_msg(bool const await_request_msg)
 	{
-		call(Call_id::SEND_REPLY_MSG, await_request_msg);
+		return call(Call_id::SEND_REPLY_MSG, await_request_msg);
 	}
 
 
diff --git a/base-hw/src/base/ipc.cc b/base-hw/src/base/ipc.cc
index 130d5b0607..fbf9a77858 100644
--- a/base-hw/src/base/ipc.cc
+++ b/base-hw/src/base/ipc.cc
@@ -116,14 +116,10 @@ Ipc_istream::~Ipc_istream() { }
 
 void Ipc_client::_call()
 {
-	/* send request */
+	/* send request and receive corresponding reply */
 	unsigned const local_name = Ipc_ostream::_dst.local_name();
 	msgbuf_to_utcb(_snd_msg, _write_offset, local_name);
-	Kernel::send_request_msg(Ipc_ostream::_dst.dst());
-
-	/* receive reply */
-	Native_utcb * const utcb = Thread_base::myself()->utcb();
-	if (utcb->msg.type != Msg::Type::IPC) {
+	if (Kernel::send_request_msg(Ipc_ostream::_dst.dst())) {
 		PERR("failed to receive reply");
 		throw Blocking_canceled();
 	}
@@ -166,10 +162,8 @@ void Ipc_server::_prepare_next_reply_wait()
 
 void Ipc_server::_wait()
 {
-	/* receive next request */
-	Kernel::await_request_msg();
-	Native_utcb * const utcb = Thread_base::myself()->utcb();
-	if (utcb->msg.type != Msg::Type::IPC) {
+	/* receive request */
+	if (Kernel::await_request_msg()) {
 		PERR("failed to receive request");
 		throw Blocking_canceled();
 	}
@@ -195,14 +189,10 @@ void Ipc_server::_reply_wait()
 		_wait();
 		return;
 	}
-	/* send reply an await request */
+	/* send reply and receive next request */
 	unsigned const local_name = Ipc_ostream::_dst.local_name();
 	msgbuf_to_utcb(_snd_msg, _write_offset, local_name);
-	Kernel::send_reply_msg(1);
-
-	/* fetch request */
-	Native_utcb * const utcb = Thread_base::myself()->utcb();
-	if (utcb->msg.type != Msg::Type::IPC) {
+	if (Kernel::send_reply_msg(1)) {
 		PERR("failed to receive request");
 		throw Blocking_canceled();
 	}
@@ -211,4 +201,3 @@ void Ipc_server::_reply_wait()
 	/* update server state */
 	_prepare_next_reply_wait();
 }
-
diff --git a/base-hw/src/core/kernel/thread.cc b/base-hw/src/core/kernel/thread.cc
index 23c5c312de..7849a94289 100644
--- a/base-hw/src/core/kernel/thread.cc
+++ b/base-hw/src/core/kernel/thread.cc
@@ -84,6 +84,7 @@ void Thread::_received_ipc_request(size_t const s)
 {
 	switch (_state) {
 	case SCHEDULED:
+		user_arg_0(0);
 		return;
 	default:
 		PERR("wrong thread state to receive IPC");
@@ -112,6 +113,7 @@ void Thread::_await_ipc_succeeded(size_t const s)
 {
 	switch (_state) {
 	case AWAITS_IPC:
+		user_arg_0(0);
 		_schedule();
 		return;
 	default:
@@ -126,6 +128,7 @@ void Thread::_await_ipc_failed()
 {
 	switch (_state) {
 	case AWAITS_IPC:
+		user_arg_0(-1);
 		_schedule();
 		return;
 	case SCHEDULED:
@@ -485,6 +488,7 @@ void Thread::_call_send_reply_msg()
 	Ipc_node::send_reply(msg_base, msg_size);
 	bool const await_request_msg = user_arg_1();
 	if (await_request_msg) { _call_await_request_msg(); }
+	else { user_arg_0(0); }
 }