diff --git a/calendar/inc/class.uiviews.inc.php b/calendar/inc/class.uiviews.inc.php
index 6d232e9a58..515e9ee52d 100644
--- a/calendar/inc/class.uiviews.inc.php
+++ b/calendar/inc/class.uiviews.inc.php
@@ -295,7 +295,7 @@ class uiviews extends uical
 	{
 		if ($this->debug > 0) $this->bo->debug_message('uiviews::month(weeks=%1) date=%2',True,$weeks,$this->date);
 
-		$this->use_time_grid = $this->cal_prefs['use_time_grid'] == 'all';	// all views
+		$this->use_time_grid = !$this->cal_prefs['use_time_grid'] || $this->cal_prefs['use_time_grid'] == 'all';	// all views
 
 		if ($weeks)
 		{