diff --git a/install/ui/ipa.js b/install/ui/ipa.js
index 4fb0559b9..0c25863d7 100644
--- a/install/ui/ipa.js
+++ b/install/ui/ipa.js
@@ -194,7 +194,9 @@ var IPA = function() {
             ],
             on_success: function(data, text_status, xhr) {
                 IPA.ui.initialized = true;
-                params.on_success.call(this, data, text_status, xhr);
+                if (params.on_success) {
+                    params.on_success.call(this, data, text_status, xhr);
+                }
             },
             on_error: params.on_error
         });