diff --git a/include/kernel.h b/include/kernel.h
index c0ecb882600..139496cf234 100644
--- a/include/kernel.h
+++ b/include/kernel.h
@@ -644,6 +644,8 @@ __syscall int k_thread_join(struct k_thread *thread, k_timeout_t timeout);
  * This routine puts the current thread to sleep for @a duration,
  * specified as a k_timeout_t object.
  *
+ * @note if @a timeout is set to K_FOREVER then the thread is suspended.
+ *
  * @param timeout Desired duration of sleep.
  *
  * @return Zero if the requested time has elapsed or the number of milliseconds
diff --git a/kernel/sched.c b/kernel/sched.c
index a3bd2614f71..57566a631d8 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1310,6 +1310,7 @@ int32_t z_impl_k_sleep(k_timeout_t timeout)
 	__ASSERT(!arch_is_in_isr(), "");
 	sys_trace_void(SYS_TRACE_ID_SLEEP);
 
+	/* in case of K_FOREVER, we suspend */
 	if (K_TIMEOUT_EQ(timeout, K_FOREVER)) {
 		k_thread_suspend(_current);
 		return (int32_t) K_TICKS_FOREVER;