diff --git a/tests/test_client.py b/tests/test_client.py
index 39b11e2..5ae21f3 100644
--- a/tests/test_client.py
+++ b/tests/test_client.py
@@ -1154,13 +1154,15 @@ def test_api_key_auth(self):
 
         response = mock.Mock()
         response.status_code = 200
-        response.json.return_value = {}
+        response.text = "OPML feed"
 
         session.get = mock.Mock()
         session.get.return_value = response
 
         client = miniflux.Client("http://localhost", api_key="secret", session=session)
-        client.export()
+        result = client.export()
+
+        self.assertEqual(result, "OPML feed")
 
         session.get.assert_called_once_with(
             "http://localhost/v1/export",