diff --git a/src/pretix/static/pretixbase/js/asynctask.js b/src/pretix/static/pretixbase/js/asynctask.js
index a720a3b182..b8924ecd0a 100644
--- a/src/pretix/static/pretixbase/js/asynctask.js
+++ b/src/pretix/static/pretixbase/js/asynctask.js
@@ -330,9 +330,11 @@ var ajaxErrDialog = {
         $("#ajaxerr .links").html("<a class='btn btn-default ajaxerr-close'>"
                                   + gettext("Close message") + "</a>");
         $("body").addClass("ajaxerr has-modal-dialog");
+        $("#ajaxerr").prop("hidden", false);
     },
     hide: function () {
         "use strict";
         $("body").removeClass("ajaxerr has-modal-dialog");
+        $("#ajaxerr").prop("hidden", true);
     },
 };
diff --git a/src/pretix/static/pretixcontrol/js/ui/main.js b/src/pretix/static/pretixcontrol/js/ui/main.js
index 7ac5db7dcb..95f321fe8d 100644
--- a/src/pretix/static/pretixcontrol/js/ui/main.js
+++ b/src/pretix/static/pretixcontrol/js/ui/main.js
@@ -60,7 +60,7 @@ var i18nToString = function (i18nstring) {
 $(document).ajaxError(function (event, jqXHR, settings, thrownError) {
     waitingDialog.hide();
     var c = $(jqXHR.responseText).filter('.container');
-    if (jqXHR.responseText.indexOf("<!-- pretix-login-marker -->") !== -1) {
+    if (jqXHR.responseText && jqXHR.responseText.indexOf("<!-- pretix-login-marker -->") !== -1) {
         location.href = '/control/login?next=' + encodeURIComponent(location.pathname + location.search + location.hash)
     } else if (c.length > 0) {
         ajaxErrDialog.show(c.first().html());