diff --git a/lib/business/calendar.rb b/lib/business/calendar.rb
index 4815c7d..8946c05 100644
--- a/lib/business/calendar.rb
+++ b/lib/business/calendar.rb
@@ -57,6 +57,10 @@ def initialize(config)
       set_extra_working_dates(config[:extra_working_dates])
       set_working_days(config[:working_days])
       set_holidays(config[:holidays])
+
+      unless (@holidays & @extra_working_dates).none?
+        raise ArgumentError, 'Holidays cannot be extra working dates'
+      end
     end
 
     # Return true if the date given is a business day (typically that means a
@@ -197,8 +201,6 @@ def parse_dates(dates)
     # Internal method for assigning holidays from a calendar config.
     def set_holidays(holidays)
       @holidays = parse_dates(holidays)
-      return if (@holidays & @extra_working_dates).none?
-      raise ArgumentError, 'Holidays cannot be extra working dates'
     end
 
     def set_extra_working_dates(extra_working_dates)