diff --git a/quad/quadwriter/lang-helper.rkt b/quad/quadwriter/lang-helper.rkt
index 4f5a3d3d..1727ae04 100644
--- a/quad/quadwriter/lang-helper.rkt
+++ b/quad/quadwriter/lang-helper.rkt
@@ -56,9 +56,9 @@
               (define (VIEW-RESULT)
                 (define open-string
                   (case (system-type 'os)
-                    [(macosx) "open ~a"]
-                    [(windows) "start ~a"]
-                    [(unix) "xdg-open ~a &> /dev/null"]
+                    [(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)))))