diff --git a/airflow/api_connexion/endpoints/user_endpoint.py b/airflow/api_connexion/endpoints/user_endpoint.py
index 506e11e00612c..a9482701a48fa 100644
--- a/airflow/api_connexion/endpoints/user_endpoint.py
+++ b/airflow/api_connexion/endpoints/user_endpoint.py
@@ -119,7 +119,7 @@ def post_user() -> APIResponse:
     user = security_manager.add_user(role=roles_to_add, **data)
     if not user:
         detail = f"Failed to add user `{username}`."
-        return Unknown(detail=detail)
+        raise Unknown(detail=detail)
 
     return user_schema.dump(user)
 
diff --git a/tests/api_connexion/endpoints/test_user_endpoint.py b/tests/api_connexion/endpoints/test_user_endpoint.py
index c56c989b34146..a84b7f1087afc 100644
--- a/tests/api_connexion/endpoints/test_user_endpoint.py
+++ b/tests/api_connexion/endpoints/test_user_endpoint.py
@@ -525,6 +525,20 @@ def test_invalid_payload(self, autoclean_user_payload, payload_converter, error_
             "type": EXCEPTIONS_LINK_MAP[400],
         }
 
+    def test_internal_server_error(self, autoclean_user_payload):
+        with unittest.mock.patch.object(self.app.appbuilder.sm, "add_user", return_value=None):
+            response = self.client.post(
+                "/api/v1/users",
+                json=autoclean_user_payload,
+                environ_overrides={"REMOTE_USER": "test"},
+            )
+            assert response.json == {
+                "detail": "Failed to add user `example_user`.",
+                "status": 500,
+                "title": "Internal Server Error",
+                "type": EXCEPTIONS_LINK_MAP[500],
+            }
+
 
 class TestPatchUser(TestUserEndpoint):
     @pytest.mark.usefixtures("autoclean_admin_user")