diff --git a/calendar/inc/class.calendar_uiforms.inc.php b/calendar/inc/class.calendar_uiforms.inc.php
index 37b047e681..c1863bc176 100644
--- a/calendar/inc/class.calendar_uiforms.inc.php
+++ b/calendar/inc/class.calendar_uiforms.inc.php
@@ -1883,9 +1883,9 @@ class calendar_uiforms extends calendar_ui
 				$readonlys['recur_interval'] = $readonlys['recur_data'] = true;
 			}
 		}
-		if($content['category'] && !is_array($content['category']))
+		if ($content['category'] && !is_array($content['category']))
 		{
-			$content['category'] = explode(',',$event['category']);
+			$content['category'] = explode(',', $content['category']);
 		}
 		// disabling the custom fields tab, if there are none
 		$readonlys['tabs'] = array(