diff --git a/src/threads/thread.c b/src/threads/thread.c
index 6b48788..6c1dcca 100644
--- a/src/threads/thread.c
+++ b/src/threads/thread.c
@@ -358,6 +358,7 @@ thread_set_priority (int new_priority)
 {
   ASSERT (PRI_MIN <= new_priority && new_priority <= PRI_MAX);
   thread_current ()->priority = new_priority;
+  thread_yield ();
 }
 
 /* Returns the current thread's priority. */