diff --git a/CHANGES.rst b/CHANGES.rst
index a28c7f7a61..2412a02f92 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -26,7 +26,7 @@ Bugfixes
   native ``str`` on both Python versions.
   (`#265 <https://github.com/zopefoundation/Zope/pull/265>`_)
 
-- Inlcude the ``zmi.styles`` repository in this package to break a circular
+- Include the ``zmi.styles`` repository in this package to break a circular
   dependency.
   (`#307 <https://github.com/zopefoundation/Zope/pull/307>`_)
 
diff --git a/src/zmi/styles/resources/zmi_base.js b/src/zmi/styles/resources/zmi_base.js
index 8b6b65ff48..8857b2e51c 100644
--- a/src/zmi/styles/resources/zmi_base.js
+++ b/src/zmi/styles/resources/zmi_base.js
@@ -13,10 +13,15 @@ function toggle_menu() {
 
 // [2] Add New Object Item (with Modal Dialog)
 function addItem( elm, base_url ) {
+	// e.g. manage_addProduct/OFSP/folderAdd
 	var url_action =  elm.options[elm.selectedIndex].value;
+	// http://localhost/myfolder/manage_addProduct/OFSP/folderAdd
 	var url_full = base_url + '/' + url_action;
-	var action = url_action.split('/')[url_action.split('/').length-1];
-	var modal_form_base = url_full.split(action)[0];
+	var parts = url_action.split('/');
+	// folderAdd
+	var action = parts[parts.length-1];
+	// http://localhost/myfolder/manage_addProduct/OFSP/
+	var modal_form_base = url_full.slice(0, -action.length);
 	var modal_body_url = url_full + '?zmi_dialog=modal';
 
 	// List of Object Types Inserting Without Modal Dialog