diff --git a/src/threads/thread.c b/src/threads/thread.c
index 5bca536..4ddee22 100644
--- a/src/threads/thread.c
+++ b/src/threads/thread.c
@@ -374,6 +374,9 @@ priority_more (const struct list_elem *a_, const struct list_elem *b_,
 void
 thread_set_priority (int new_priority) 
 {
+  ASSERT (new_priority >= PRI_MIN);
+  ASSERT (new_priority <= PRI_MAX);
+
   thread_current ()->priority = new_priority;
 }