diff --git a/counter/models.py b/counter/models.py
index 3640c3f5..18215856 100644
--- a/counter/models.py
+++ b/counter/models.py
@@ -652,13 +652,12 @@ class Counter(models.Model):
         )["total"]
 
     def customer_is_barman(self, customer: Customer | User) -> bool:
-        """Check if current counter is a `bar` and that the customer is on the barmen_list
+        """Check if this counter is a `bar` and if the customer is currently logged in.
+        This is useful to compute special prices."""
 
-        This is useful to compute special prices"""
-        if isinstance(customer, Customer):
-            customer: User = customer.user
-
-        return self.type == "BAR" and customer in self.barmen_list
+        # Customer and User are two different tables,
+        # but they share the same primary key
+        return self.type == "BAR" and any(b.pk == customer.pk for b in self.barmen_list)
 
 
 class RefillingQuerySet(models.QuerySet):
diff --git a/counter/views/click.py b/counter/views/click.py
index c6bafa57..9542b467 100644
--- a/counter/views/click.py
+++ b/counter/views/click.py
@@ -417,7 +417,7 @@ class RefillingCreateView(FormView):
     def get_template_data(
         cls, customer: Customer, *, form_instance: form_class | None = None
     ) -> FormFragmentTemplateData[form_class]:
-        return FormFragmentTemplateData[cls.form_class](
+        return FormFragmentTemplateData(
             form=form_instance if form_instance else cls.form_class(),
             template=cls.template_name,
             context={
diff --git a/counter/views/student_card.py b/counter/views/student_card.py
index 952f65eb..f916260b 100644
--- a/counter/views/student_card.py
+++ b/counter/views/student_card.py
@@ -73,7 +73,7 @@ class StudentCardFormView(FormView):
         cls, customer: Customer, *, form_instance: form_class | None = None
     ) -> FormFragmentTemplateData[form_class]:
         """Get necessary data to pre-render the fragment"""
-        return FormFragmentTemplateData[cls.form_class](
+        return FormFragmentTemplateData(
             form=form_instance if form_instance else cls.form_class(),
             template=cls.template_name,
             context={