diff --git a/core/misc/ajax.js b/core/misc/ajax.js
index 4a1e327..53351ad 100644
--- a/core/misc/ajax.js
+++ b/core/misc/ajax.js
@@ -566,7 +566,8 @@ Drupal.ajax.prototype.commands = {
     // @todo Consider whether this is overloading title inappropriately, and
     //   if so, find another way to determine dialog eligibility.
     if (ajax.dialog && ('title' in response)) {
-      var dialog = Drupal.dialog(wrapper, {title: response.title});
+      var dialogOptions = $.extend({title: response.title}, ajax.dialog);
+      var dialog = Drupal.dialog(wrapper, dialogOptions);
       ajax.dialog.modal ? dialog.showModal() : dialog.show();
     }
 
diff --git a/core/misc/dialog.js b/core/misc/dialog.js
index c0bccf1..a0849bc 100644
--- a/core/misc/dialog.js
+++ b/core/misc/dialog.js
@@ -30,7 +30,7 @@ Drupal.behaviors.dialog = {
 Drupal.dialog = function (element, options) {
 
   function openDialog (settings) {
-    settings = $.extend(settings, defaults);
+    settings = $.extend({}, drupalSettings.dialog, options, settings);
     // Trigger a global event to allow scripts to bind events to the dialog.
     $(window).trigger('dialog:beforecreate', [dialog, $element, settings]);
     $element.dialog(settings);
@@ -48,7 +48,6 @@ Drupal.dialog = function (element, options) {
 
   var undef;
   var $element = $(element);
-  var defaults = $.extend(options, drupalSettings.dialog);
   var dialog = {
     open: false,
     returnValue: undef,