diff --git a/collects/2htdp/batch-io.rkt b/collects/2htdp/batch-io.rkt
index 663d087388..b4af560368 100644
--- a/collects/2htdp/batch-io.rkt
+++ b/collects/2htdp/batch-io.rkt
@@ -124,6 +124,7 @@
   (let ([result (not (file-exists? f))])
     (with-output-to-file f 
       (lambda () (printf "~a" str))
+      #:mode 'text
       #:exists 'replace)
     f))