diff --git a/collects/scribblings/quick/mreval.ss b/collects/scribblings/quick/mreval.ss
index ab9eb9f56b..39c4931c1a 100644
--- a/collects/scribblings/quick/mreval.ss
+++ b/collects/scribblings/quick/mreval.ss
@@ -128,8 +128,10 @@
           (((mr-eval 'make-pict-drawer) v) dc 0 0)
           (send bm save-file fn 'png)
           (make-element #f (list (make-element (make-image-file 
-                                                ;; For HTML output, .pdf is automatically changed to .png:
-                                                (path-replace-suffix fn #".pdf")
+                                                ;; For HTML output, .pdf is automatically changed to .png.
+                                                ;; Be sure to use a string rather than a path, because
+                                                ;; it gets recorded in "exprs.dat".
+                                                (path->string (path-replace-suffix fn #".pdf"))
                                                 1.0) 
                                                (list "[image]"))))))]
      [(pair? v) (cons (fixup-picts (car v))