diff --git a/test/unit/display_utils_spec.js b/test/unit/display_utils_spec.js
index 0859107ad..c1b591ec3 100644
--- a/test/unit/display_utils_spec.js
+++ b/test/unit/display_utils_spec.js
@@ -151,6 +151,9 @@ describe("display_utils", function () {
       expect(getPdfFilenameFromUrl("/pdfs/%AA.pdf")).toEqual("%AA.pdf");
 
       expect(getPdfFilenameFromUrl("/pdfs/%2F.pdf")).toEqual("%2F.pdf");
+
+      // A corrupt relative URL.
+      expect(getPdfFilenameFromUrl("//%%file.pdf")).toEqual("document.pdf");
     });
 
     it("gets PDF filename from (some) standard protocols", function () {