diff --git a/aleksis/apps/alsijil/forms.py b/aleksis/apps/alsijil/forms.py
index ec3d51503b2e2c4881dd651aedcbe4fd80c64d9f..322de9d2fa763a3be9cec5fab8fae30c8550a1ec 100644
--- a/aleksis/apps/alsijil/forms.py
+++ b/aleksis/apps/alsijil/forms.py
@@ -275,7 +275,7 @@ class FilterRegisterObjectForm(forms.Form):
     date_end = forms.DateField(label=_("End date"))
 
     @classmethod
-    def get_initial(cls, has_documentation=None):
+    def get_initial(cls, has_documentation: Optional[bool] = None):
         date_end = timezone.now().date()
         date_start = date_end - timedelta(days=30)
         return {