diff --git a/admin/maintenance_sys.php b/admin/maintenance_sys.php
index 5a8334d77..ffc9fba6f 100644
--- a/admin/maintenance_sys.php
+++ b/admin/maintenance_sys.php
@@ -167,7 +167,11 @@ if (is_webmaster())
 
         case ACTIVITY_SYSTEM_PLUGIN:
           $object_icon = 'icon-puzzle';
-          $object = str_replace(['_', '-'], ' ', $details['plugin_id']);
+          $object = 'plugin';
+          if (isset($details['plugin_id']))
+          {
+            $object = str_replace(['_', '-'], ' ', $details['plugin_id']);
+          }
           switch ($rows['action'])
           {
             case 'install':
@@ -244,7 +248,11 @@ if (is_webmaster())
 
         case ACTIVITY_SYSTEM_THEME:
           $object_icon = 'icon-brush';
-          $object = str_replace(['_', '-'], ' ', $details['theme_id']);
+          $object = 'theme';
+          if (isset($details['theme_id']))
+          {
+            $object = str_replace(['_', '-'], ' ', $details['theme_id']);
+          }
 
           switch ($rows['action'])
           {