diff --git a/basis/listener/listener.factor b/basis/listener/listener.factor
index 122921aaa3..f388ce7a14 100644
--- a/basis/listener/listener.factor
+++ b/basis/listener/listener.factor
@@ -34,7 +34,7 @@ M: object stream-read-quot
 
 SYMBOL: visible-vars
 
-: show-var ( var -- ) visible-vars  [ swap suffix ] change ;
+: show-var ( var -- ) visible-vars [ swap suffix ] change ;
 
 : show-vars ( seq -- ) visible-vars [ swap union ] change ;