diff --git a/src/backend/core/api/__init__.py b/src/backend/core/api/__init__.py
index b72c847..57c847b 100644
--- a/src/backend/core/api/__init__.py
+++ b/src/backend/core/api/__init__.py
@@ -23,6 +23,8 @@ def exception_handler(exc, context):
             detail = exc.message
         elif hasattr(exc, "messages"):
             detail = exc.messages
+        else:
+            detail = ""
 
         exc = drf_exceptions.ValidationError(detail=detail)
 
diff --git a/src/backend/core/tests/test_api_team_invitations.py b/src/backend/core/tests/test_api_team_invitations.py
index e4c0925..d69ad67 100644
--- a/src/backend/core/tests/test_api_team_invitations.py
+++ b/src/backend/core/tests/test_api_team_invitations.py
@@ -349,6 +349,8 @@ def test_api_team_invitations__update__forbidden(method):
 
     client = APIClient()
     client.force_login(user)
+
+    response = None
     if method == "put":
         response = client.put(
             f"/api/v1.0/teams/{invitation.team.id}/invitations/{invitation.id}/",
@@ -357,6 +359,7 @@ def test_api_team_invitations__update__forbidden(method):
         response = client.patch(
             f"/api/v1.0/teams/{invitation.team.id}/invitations/{invitation.id}/",
         )
+    assert response is not None
     assert response.status_code == status.HTTP_405_METHOD_NOT_ALLOWED
     assert response.json()["detail"] == f'Method "{method.upper()}" not allowed.'