diff --git a/addons/web_calendar/static/src/js/calendar.js b/addons/web_calendar/static/src/js/calendar.js
index 9af5130a121..ce200fe4f5f 100644
--- a/addons/web_calendar/static/src/js/calendar.js
+++ b/addons/web_calendar/static/src/js/calendar.js
@@ -57,7 +57,7 @@ openerp.web_calendar.CalendarView = openerp.web.View.extend({
         this.fields =  this.fields_view.fields;
         
         if (!this.date_start) {
-            throw new Error("Calendar view has none of the following attributes : 'date_start'");
+            throw new Error("Calendar view has not defined 'date_start' attribute.");
         }
 
         //* Calendar Fields *