diff --git a/third_party/lua/README.cosmo b/third_party/lua/README.cosmo
index 1d418f797..6f02aec3c 100644
--- a/third_party/lua/README.cosmo
+++ b/third_party/lua/README.cosmo
@@ -36,3 +36,5 @@ LOCAL MODIFICATIONS
   Added Python-like printf modulus operator for strings.
 
   Added Python-like printf multiply operator for strings.
+
+  Fixed a buffer overflow in os.tmpname