diff --git a/beautiful-racket-demo/algebra-demo/main.rkt b/beautiful-racket-demo/algebra-demo/main.rkt
index b11ff54..f17f71c 100644
--- a/beautiful-racket-demo/algebra-demo/main.rkt
+++ b/beautiful-racket-demo/algebra-demo/main.rkt
@@ -30,6 +30,7 @@
 
 (define (read-syntax src ip)
   (port-count-lines! ip)
+  (lexer-file-path src)
   (define parse-tree (parse src (λ () (tokenize-1 ip))))
   (strip-bindings
    (with-syntax ([PT parse-tree])
diff --git a/beautiful-racket-demo/precalc-demo/main.rkt b/beautiful-racket-demo/precalc-demo/main.rkt
index 55baee3..f090e47 100644
--- a/beautiful-racket-demo/precalc-demo/main.rkt
+++ b/beautiful-racket-demo/precalc-demo/main.rkt
@@ -41,6 +41,7 @@
 
 (define (read-syntax src ip)
   (port-count-lines! ip)
+  (lexer-file-path src)
   (define parse-tree (parse src (λ () (tokenize-1 ip))))
   (strip-bindings
    (with-syntax ([PT parse-tree])