diff --git a/kernel/mailbox.c b/kernel/mailbox.c
index e355d724b7..1c5bb95659 100644
--- a/kernel/mailbox.c
+++ b/kernel/mailbox.c
@@ -285,8 +285,7 @@ static int mbox_message_put(struct k_mbox *mbox, struct k_mbox_msg *tx_msg,
 			 * synchronous send: pend current thread (unqueued)
 			 * until the receiver consumes the message
 			 */
-			_remove_thread_from_ready_q(_current);
-			_mark_thread_as_pending(_current);
+			_pend_current_thread(NULL, K_FOREVER);
 			return _Swap(key);
 		}
 	}
diff --git a/kernel/sched.c b/kernel/sched.c
index e7d6ec2586..34f16c2903 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -203,6 +203,10 @@ void _pend_thread(struct k_thread *thread, _wait_q_t *wait_q, s32_t timeout)
 	sys_dlist_t *wait_q_list = (sys_dlist_t *)wait_q;
 	struct k_thread *pending;
 
+	if (!wait_q_list) {
+		goto inserted;
+	}
+
 	SYS_DLIST_FOR_EACH_CONTAINER(wait_q_list, pending, base.k_q_node) {
 		if (_is_t1_higher_prio_than_t2(thread, pending)) {
 			sys_dlist_insert_before(wait_q_list,