diff --git a/calendar/inc/class.calendar_uiforms.inc.php b/calendar/inc/class.calendar_uiforms.inc.php
index 1cf7272f5d..319844bc76 100644
--- a/calendar/inc/class.calendar_uiforms.inc.php
+++ b/calendar/inc/class.calendar_uiforms.inc.php
@@ -1715,6 +1715,7 @@ class calendar_uiforms extends calendar_ui
 				$readonlys['recur_interval'] = $readonlys['recur_data'] = true;
 			}
 		}
+		$content['category'] = explode(',',$event['category']);
 		// disabling the custom fields tab, if there are none
 		$readonlys['tabs'] = array(
 			'custom' => !count($this->bo->customfields),