diff --git a/src/threads/thread.c b/src/threads/thread.c
index 6c1dcca..3a428f1 100644
--- a/src/threads/thread.c
+++ b/src/threads/thread.c
@@ -357,8 +357,11 @@ void
 thread_set_priority (int new_priority) 
 {
   ASSERT (PRI_MIN <= new_priority && new_priority <= PRI_MAX);
+  int old_priority = thread_get_priority ();
+
   thread_current ()->priority = new_priority;
-  thread_yield ();
+  if (new_priority < old_priority)
+    thread_yield ();
 }
 
 /* Returns the current thread's priority. */