diff --git a/web/app.js b/web/app.js
index 1dfb6e66c9eb08..07980c90734b84 100644
--- a/web/app.js
+++ b/web/app.js
@@ -991,18 +991,20 @@ const PDFViewerApplication = {
     const workerParams = AppOptions.getAll(OptionKind.WORKER);
     Object.assign(GlobalWorkerOptions, workerParams);
 
-    if (typeof PDFJSDev !== "undefined" && PDFJSDev.test("MOZCENTRAL")) {
-      if (args.data && isPdfFile(args.filename)) {
-        this._contentDispositionFilename = args.filename;
+    if (typeof PDFJSDev !== "undefined" && !PDFJSDev.test("MOZCENTRAL")) {
+      if (args.url) {
+        // The Firefox built-in viewer always calls `setTitleUsingUrl`, before
+        // `initPassiveLoading`, and it never provides an `originalUrl` here.
+        this.setTitleUsingUrl(
+          args.originalUrl || args.url,
+          /* downloadUrl = */ args.url
+        );
       }
-    } else if (args.url) {
-      // The Firefox built-in viewer always calls `setTitleUsingUrl`, before
-      // `initPassiveLoading`, and it never provides an `originalUrl` here.
-      this.setTitleUsingUrl(
-        args.originalUrl || args.url,
-        /* downloadUrl = */ args.url
-      );
     }
+    if (args.data && isPdfFile(args.filename)) {
+      this._contentDispositionFilename = args.filename;
+    }
+
     // Always set `docBaseUrl` in development mode, and in the (various)
     // extension builds.
     if (typeof PDFJSDev === "undefined") {