diff --git a/src/threads/thread.c b/src/threads/thread.c
index 230789e..6657d9f 100644
--- a/src/threads/thread.c
+++ b/src/threads/thread.c
@@ -382,6 +382,8 @@ thread_foreach (thread_action_func *func, void *aux)
 void
 thread_set_priority (int new_priority) 
 {
+  if (thread_mlfqs)
+    return;
   thread_current ()->priority = new_priority;
 }