diff --git a/ludus.grammar b/ludus.grammar
index a29b29e..0d5952a 100644
--- a/ludus.grammar
+++ b/ludus.grammar
@@ -26,7 +26,7 @@ expression { non_binding | binding }
 
 binding { Let | Ref | Fn_Named | Fn_Compound }
 
-Ref { silent<"ref"> Word "=" expression }
+Ref { silent<"box"> Word "=" expression }
 
 non_binding { simple | complex }