Index: units/categories/categories_event_handler.php
===================================================================
--- units/categories/categories_event_handler.php	(revision 15359)
+++ units/categories/categories_event_handler.php	(working copy)
@@ -2814,12 +2814,18 @@
 				$template = 'index';
 			}
 
-			// remove template from url if it is category index cached template OR site homepage
-			if (($template == $category_template) || (mb_strtolower($template) == '__default__') || ($template == 'index')) {
-				// given template is also default template for this category OR '__default__' given OR site homepage
+			// remove template from url if it is category index cached template
+			if ( ($template == $category_template) || (mb_strtolower($template) == '__default__') ) {
+				// given template is also default template for this category OR '__default__' given
 				$params['pass_template'] = false;
 			}
 
+			// remove template from url if it is site homepage on primary language & theme
+			if ( ($template == 'index') && $processed_params['m_lang'] == $rewrite_processor->primaryLanguageId && $processed_params['m_theme'] == $rewrite_processor->primaryThemeId ) {
+				// given template is site homepage on primary language & theme
+				$params['pass_template'] = false;
+			}
+
 			if ($template && $params['pass_template']) {
 				$ret .= $template . '/';
 			}