diff --git a/tools/bars.janet b/tools/bars.janet
index a5826ea6..1f573d6e 100644
--- a/tools/bars.janet
+++ b/tools/bars.janet
@@ -47,7 +47,7 @@
     :error (error (parser/error p)))
 
   # Make ast from forms
-  (def ast ~(fn [params &] (default params @{}) (,buffer ,;forms)))
+  (def ast ~(fn [&opt params] (default params @{}) (,buffer ,;forms)))
 
   (def ctor (compile ast *env* source))
   (if-not (function? ctor)