diff --git a/src/accounting/models.py b/src/accounting/models.py
index c6d1362..9db46eb 100644
--- a/src/accounting/models.py
+++ b/src/accounting/models.py
@@ -88,7 +88,7 @@ class Order(CreatedModifiedAbstract):
         verbose_name = pgettext_lazy("accounting term", "Order")
         verbose_name_plural = pgettext_lazy("accounting term", "Orders")
 
-    def __str__(self):
+    def __str__(self) -> str:
         return f"Order ID {self.display_id}"
 
 
@@ -113,7 +113,7 @@ class Payment(CreatedModifiedAbstract):
             description=order.description,
         )
 
-    def __str__(self):
+    def __str__(self) -> str:
         return f"Payment ID {self.display_id}"
 
     class Meta:
diff --git a/src/accounting/tests.py b/src/accounting/tests.py
index 0aebd0c..d2ab2bd 100644
--- a/src/accounting/tests.py
+++ b/src/accounting/tests.py
@@ -9,7 +9,7 @@ from . import models
 
 
 @pytest.mark.django_db()
-def test_balance():
+def test_balance() -> None:
     user = User.objects.create_user("test", "lala@adas.com", "1234")
     account = models.Account.objects.create(owner=user)
     assert account.balance == 0
diff --git a/src/membership/__init__.py b/src/membership/__init__.py
index f9e27aa..f5e828a 100644
--- a/src/membership/__init__.py
+++ b/src/membership/__init__.py
@@ -1,4 +1,4 @@
-"""Membership application
+"""Membership application.
 ======================
 
 This application's domain relate to organizational structures and
diff --git a/src/membership/apps.py b/src/membership/apps.py
index 5248df4..b8459a2 100644
--- a/src/membership/apps.py
+++ b/src/membership/apps.py
@@ -5,7 +5,7 @@ from django.db.models.signals import post_migrate
 class MembershipConfig(AppConfig):
     name = "membership"
 
-    def ready(self):
+    def ready(self) -> None:
         from .permissions import persist_permissions
 
         post_migrate.connect(persist_permissions, sender=self)
diff --git a/src/membership/models.py b/src/membership/models.py
index d61e157..730133f 100644
--- a/src/membership/models.py
+++ b/src/membership/models.py
@@ -48,7 +48,7 @@ class SubscriptionPeriod(CreatedModifiedAbstract):
             ),
         ]
 
-    def __str__(self):
+    def __str__(self) -> str:
         return f"{self.period.lower} - {self.period.upper or _('next general assembly')}"
 
 
@@ -94,7 +94,7 @@ class Membership(CreatedModifiedAbstract):
         on_delete=models.PROTECT,
     )
 
-    def __str__(self):
+    def __str__(self) -> str:
         return f"{self.user} - {self.period}"
 
 
@@ -109,5 +109,5 @@ class MembershipType(CreatedModifiedAbstract):
 
     name = models.CharField(verbose_name=_("name"), max_length=64)
 
-    def __str__(self):
+    def __str__(self) -> str:
         return self.name
diff --git a/src/membership/permissions.py b/src/membership/permissions.py
index 804bcef..657adcb 100644
--- a/src/membership/permissions.py
+++ b/src/membership/permissions.py
@@ -7,7 +7,7 @@ from django.utils.translation import gettext_lazy as _
 PERMISSIONS = []
 
 
-def persist_permissions(sender, **kwargs):
+def persist_permissions(sender, **kwargs) -> None:
     for permission in PERMISSIONS:
         permission.persist_permission()
 
@@ -23,10 +23,10 @@ class Permission:
         PERMISSIONS.append(self)
 
     @property
-    def path(self):
+    def path(self) -> str:
         return f"{self.app_label}.{self.codename}"
 
-    def persist_permission(self):
+    def persist_permission(self) -> None:
         content_type, _ = ContentType.objects.get_or_create(
             app_label=self.app_label,
             model=self.model,
diff --git a/src/project/urls.py b/src/project/urls.py
index 17e788b..8de19c6 100644
--- a/src/project/urls.py
+++ b/src/project/urls.py
@@ -1,4 +1,4 @@
-"""URLs for the membersystem"""
+"""URLs for the membersystem."""
 from django.conf import settings
 from django.contrib import admin
 from django.urls import include
@@ -15,4 +15,5 @@ if settings.DEBUG:
     urlpatterns = [
         path("__debug__/", include("debug_toolbar.urls")),
         path("__reload__/", include("django_browser_reload.urls")),
-    ] + urlpatterns
+        *urlpatterns,
+    ]
diff --git a/src/utils/templatetags/utils.py b/src/utils/templatetags/utils.py
index 8050639..90ab6ef 100644
--- a/src/utils/templatetags/utils.py
+++ b/src/utils/templatetags/utils.py
@@ -18,3 +18,4 @@ def active_path(context, path_name, class_name) -> str | None:
 
     if is_path or is_base_path:
         return class_name
+    return None
diff --git a/src/utils/view_utils.py b/src/utils/view_utils.py
index b48d126..3de84c3 100644
--- a/src/utils/view_utils.py
+++ b/src/utils/view_utils.py
@@ -1,17 +1,20 @@
 import contextlib
 from dataclasses import dataclass
+from typing import TYPE_CHECKING
 from typing import Any
 
 from django.contrib.sites.shortcuts import get_current_site
 from django.core.exceptions import FieldError
 from django.core.paginator import Paginator
-from django.db.models import Model
 from django.http import HttpRequest
 from django.http import HttpResponse
 from django.urls import reverse
 from zen_queries import queries_disabled
 from zen_queries import render as zen_queries_render
 
+if TYPE_CHECKING:
+    from django.db.models import Model
+
 
 @dataclass
 class Row: