diff --git a/brewman/models/voucher.py b/brewman/models/voucher.py
index 9e727628..e484d7cb 100644
--- a/brewman/models/voucher.py
+++ b/brewman/models/voucher.py
@@ -297,7 +297,7 @@ class Attendance(Base):
     def create(self):
         old = DBSession.query(Attendance).filter(Attendance.date == self.date) \
             .filter(Attendance.employee_id == self.employee_id) \
-            .filter(Attendance.is_valid is True).first()
+            .filter(Attendance.is_valid == True).first()
         if old is None or old.attendance_type != self.attendance_type:
             if old is not None:
                 old.is_valid = False