diff --git a/pylast/__init__.py b/pylast/__init__.py
index 35835f8..d075fd8 100644
--- a/pylast/__init__.py
+++ b/pylast/__init__.py
@@ -76,7 +76,8 @@ EVENT_MAYBE_ATTENDING = '1'
 EVENT_NOT_ATTENDING = '2'
 
 PERIOD_OVERALL = 'overall'
-PERIOD_7DAYS = "7day"
+PERIOD_7DAYS = '7day'
+PERIOD_1MONTHS = '1month'
 PERIOD_3MONTHS = '3month'
 PERIOD_6MONTHS = '6month'
 PERIOD_12MONTHS = '12month'