diff --git a/code/list-error.sld b/code/list-error.sld
index e7c65d9..eb388af 100644
--- a/code/list-error.sld
+++ b/code/list-error.sld
@@ -32,4 +32,6 @@
 
     (define (dotted-list-error? obj)
       (and (list-error? obj)
-           (not (null-or-pair? (list-error-tail obj)))))))
+           (let ((tail (list-error-tail obj)))
+             (not (or (null? tail)
+                      (pair? tail))))))))