diff --git a/lib/apscheduler/triggers/cron/expressions.py b/lib/apscheduler/triggers/cron/expressions.py
index 55a37167..fe3acdd9 100644
--- a/lib/apscheduler/triggers/cron/expressions.py
+++ b/lib/apscheduler/triggers/cron/expressions.py
@@ -9,7 +9,7 @@ __all__ = ('AllExpression', 'RangeExpression', 'WeekdayRangeExpression',
            'WeekdayPositionExpression', 'LastDayOfMonthExpression')
 
 
-WEEKDAYS = ['mon', 'tue', 'wed', 'thu', 'fri', 'sat', 'sun']
+WEEKDAYS = ['sun', 'mon', 'tue', 'wed', 'thu', 'fri', 'sat']
 MONTHS = ['jan', 'feb', 'mar', 'apr', 'may', 'jun', 'jul', 'aug', 'sep', 'oct', 'nov', 'dec']