diff --git a/beautiful-racket-demo/basic-demo/lexer-test.rkt b/beautiful-racket-demo/basic-demo/lexer-test.rkt
index 96e4642..ddc9bf0 100644
--- a/beautiful-racket-demo/basic-demo/lexer-test.rkt
+++ b/beautiful-racket-demo/basic-demo/lexer-test.rkt
@@ -2,7 +2,7 @@
 (require "lexer.rkt" brag/support rackunit)
 
 (define (lex str)
-  (apply-lexer basic-lexer str))
+  (apply-port-proc basic-lexer str))
 
 (check-equal? (lex "") empty)
 (check-equal?