diff --git a/kernel/mars_client.c b/kernel/mars_client.c
index 6d9eff79..20df4434 100644
--- a/kernel/mars_client.c
+++ b/kernel/mars_client.c
@@ -772,6 +772,8 @@ static int sender_thread(void *data)
 	struct client_brick *brick = output->brick;
 	struct client_channel *ch = NULL;
 	bool do_timeout = false;
+	bool cork = false;
+	bool old_cork;
 	int ch_skip = max_client_bulk;
 	int status = -ESHUTDOWN;
 	unsigned long flags;
@@ -782,7 +784,6 @@ static int sender_thread(void *data)
 		struct mref_object *mref;
 		int min_nr;
 		int max_nr;
-		bool cork;
 
 		// timeouting is a rather expensive operation, don't do it too often
 		if (do_timeout) {
@@ -798,6 +799,11 @@ static int sender_thread(void *data)
 
 
 		if (output->get_info) {
+			if (ch && old_cork) {
+				/* flush old buffer */
+				old_cork = false;
+				mars_send_raw(&ch->socket, NULL, 0, false);
+			}
 			ch = _get_channel(bundle, 0, 1);
 			if (unlikely(!ch)) {
 				do_timeout = true;
@@ -856,6 +862,11 @@ static int sender_thread(void *data)
 		    !mars_socket_is_alive(&ch->socket))
 			do_timeout = true;
 		if (do_timeout || ch->ch_nr >= max_nr || --ch_skip < 0) {
+			if (ch && old_cork) {
+				/* flush old buffer */
+				old_cork = false;
+				mars_send_raw(&ch->socket, NULL, 0, false);
+			}
 			ch = _get_channel(bundle, min_nr, max_nr);
 			if (unlikely(!ch)) {
 				// notice: this will re-assign hash_head without harm
@@ -876,6 +887,7 @@ static int sender_thread(void *data)
 		spin_unlock(&output->lock);
 
 		status = mars_send_mref(&ch->socket, mref, cork);
+		old_cork = cork;
 		if (unlikely(status < 0)) {
 			_hash_insert(output, mref_a);
 			do_timeout = true;
diff --git a/kernel/mars_net.c b/kernel/mars_net.c
index 750f69bc..bc70cade 100644
--- a/kernel/mars_net.c
+++ b/kernel/mars_net.c
@@ -515,9 +515,11 @@ restart:
 	}
 
 	if (msock->s_pos + rest < PAGE_SIZE) {
-		memcpy(msock->s_buffer + msock->s_pos, buf, rest);
-		msock->s_pos += rest;
-		sent += rest;
+		if (buf) {
+			memcpy(msock->s_buffer + msock->s_pos, buf, rest);
+			msock->s_pos += rest;
+			sent += rest;
+		}
 		rest = 0;
 		status = sent;
 		if (cork)