diff --git a/aleksis/apps/alsijil/views.py b/aleksis/apps/alsijil/views.py
index b4ad6650066431531fda7e55a128f69b53156410..68d90185ab7bb5270165c281199c233a7d2ff34c 100644
--- a/aleksis/apps/alsijil/views.py
+++ b/aleksis/apps/alsijil/views.py
@@ -55,7 +55,7 @@ def lesson(
     else:
         wanted_week = None
 
-    if not (year and week and period_id):
+    if not all((year, week, period_id)):
         if lesson_period:
             return redirect(
                 "lesson_by_week_and_period",