diff --git a/lang/en/calendar.php b/lang/en/calendar.php
index 6b27cdf25e3..5aef41c761b 100644
--- a/lang/en/calendar.php
+++ b/lang/en/calendar.php
@@ -86,7 +86,7 @@ $string['groupevent'] = 'Group event';
 $string['groupevents'] = 'Group events';
 $string['hidden'] = 'hidden';
 $string['ical'] = 'iCal';
-$string['invalidtimedurationminutes'] = 'The duration in minutes you have entered in invalid please enter the duration in minutes greater than 0 or select no duration.';
+$string['invalidtimedurationminutes'] = 'The duration in minutes you have entered is invalid. Please enter the duration in minutes greater than 0 or select no duration.';
 $string['invalidtimedurationuntil'] = 'The date and time you selected for duration until is before the start time of the event. Please correct this before proceeding.';
 $string['iwanttoexport'] = 'Export';
 $string['manyevents'] = '{$a} events';