diff --git a/quad/quadwriter/lang-helper.rkt b/quad/quadwriter/lang-helper.rkt
index 811faa0c..763c04c0 100644
--- a/quad/quadwriter/lang-helper.rkt
+++ b/quad/quadwriter/lang-helper.rkt
@@ -36,9 +36,10 @@
               (define (VIEW-RESULT)
                 (define open-string
                   (case (system-type 'os)
-                    ('macosx "open ~a")
-                    ('unix   "xdg-open ~a &> /dev/null")
-                    (else (error "Don't know how to open PDF file."))))
+                    ['macosx "open ~a"]
+                    ['windows "start ~a"]
+                    ['unix   "xdg-open ~a &> /dev/null"]
+                    [else (error "Don't know how to open PDF file.")]))
                 (when (file-exists? pdf-path)
                   (void (system (format open-string pdf-path)))))
               (module+ main