diff --git a/runtime/thread_pool.cc b/runtime/thread_pool.cc
index 2a82285..ce76eae 100644
--- a/runtime/thread_pool.cc
+++ b/runtime/thread_pool.cc
@@ -158,7 +158,7 @@
     --waiting_count_;
   }
 
-  // We are shutting down, return nullptr to tell the worker thread to stop looping.
+  // We are shutting down, return null to tell the worker thread to stop looping.
   return nullptr;
 }