diff --git a/tool/playground/T.g b/tool/playground/T.g
index 2ad228a87..c736f9fc0 100644
--- a/tool/playground/T.g
+++ b/tool/playground/T.g
@@ -1,2 +1,3 @@
-lexer grammar T;
+grammar T;
+s : A ;
 A : 'a';