diff --git a/calendar/teachingdates/calendars/basecalendar.py b/calendar/teachingdates/calendars/basecalendar.py
index 98d1cb9..c978b6f 100644
--- a/calendar/teachingdates/calendars/basecalendar.py
+++ b/calendar/teachingdates/calendars/basecalendar.py
@@ -59,9 +59,9 @@
 
         self.period_weeks = {}
         self.calendars = {}
-        for period in self.config.config.keys():
+        for period in self.config.get_config_keys():
             self.period_weeks[period] = self.generate_period_weeks(
-                self.config.config[period]["weeks"])
+                self.config.get_period_config(period)["weeks"])
             self.calendars[period] = self.generate_calendar(period)
         self.period_weeks["iso"] = self.generate_period_weeks(
             [{"iso": [