diff --git a/wagtail/admin/static_src/wagtailadmin/js/modal-workflow.js b/wagtail/admin/static_src/wagtailadmin/js/modal-workflow.js
index 1009712f2..31b4caf77 100644
--- a/wagtail/admin/static_src/wagtailadmin/js/modal-workflow.js
+++ b/wagtail/admin/static_src/wagtailadmin/js/modal-workflow.js
@@ -12,6 +12,7 @@ function ModalWorkflow(opts) {
 
     var self = {};
     var responseCallbacks = opts.responses || {};
+    var errorCallback = opts.onError || function () {};
 
     /* remove any previous modals before continuing (closing doesn't remove them from the dom) */
     $('body > .modal').remove();
@@ -26,11 +27,11 @@ function ModalWorkflow(opts) {
     self.body = container.find('.modal-body');
 
     self.loadUrl = function(url, urlParams) {
-        $.get(url, urlParams, self.loadResponseText, 'text');
+        $.get(url, urlParams, self.loadResponseText, 'text').fail(errorCallback);
     };
 
     self.postForm = function(url, formData) {
-        $.post(url, formData, self.loadResponseText, 'text');
+        $.post(url, formData, self.loadResponseText, 'text').fail(errorCallback);
     };
 
     self.ajaxifyForm = function(formSelector) {