diff --git a/src/interpreter.janet b/src/interpreter.janet
index e040e40..3f59fce 100644
--- a/src/interpreter.janet
+++ b/src/interpreter.janet
@@ -463,7 +463,8 @@
     [:dict :keyword] (get prev curr :^nil)
     [:nil :keyword] :^nil
     [:pkg :keyword] (get prev curr :^nil)
-    [:pkg :pkg-kw] (get prev curr :^nil)))
+    [:pkg :pkg-kw] (get prev curr :^nil)
+    (error (string "cannot call " (b/ludus/type prev) " `" (b/show prev) "`"))))
 
 (defn- synthetic [ast ctx]
   (def terms (ast :data))