diff --git a/plugins/calendar/drivers/kolab/kolab_driver.php b/plugins/calendar/drivers/kolab/kolab_driver.php
index 9e8f21af..2269aeb5 100644
--- a/plugins/calendar/drivers/kolab/kolab_driver.php
+++ b/plugins/calendar/drivers/kolab/kolab_driver.php
@@ -120,6 +120,27 @@ class kolab_driver extends calendar_driver
     return false;
   }
 
+  /**
+   * Update properties of an existing calendar
+   *
+   * @see calendar_driver::edit_calendar()
+   */
+  public function edit_calendar($prop)
+  {
+    return false;
+  }
+
+  /**
+   * Delete the given calendar with all its contents
+   *
+   * @see calendar_driver::remove_calendar()
+   */
+  public function remove_calendar($prop)
+  {
+    return false;
+  }
+
+
   /**
    * Add a single event to the database
    *