diff --git a/tests/test_integration_users.py b/tests/test_integration_users.py
index eb38b6c..4c1cc01 100644
--- a/tests/test_integration_users.py
+++ b/tests/test_integration_users.py
@@ -97,6 +97,7 @@ def test_client_raises_without_key(self, monkeypatch: pytest.MonkeyPatch) -> Non
         """Client should raise ConfigurationError when no API key exists."""
         monkeypatch.delenv("BG_API_KEY", raising=False)
         # Patch _load_api_key to ensure no config file fallback
+        monkeypatch.setattr(Configuration, "_load_api_key", lambda _self: None)
         with pytest.raises(ConfigurationError):
             Client(api_key=None)
 
@@ -105,6 +106,7 @@ def test_whitespace_only_api_key_rejected(
     ) -> None:
         """Whitespace-only API key should be rejected by Client."""
         monkeypatch.delenv("BG_API_KEY", raising=False)
+        monkeypatch.setattr(Configuration, "_load_api_key", lambda _self: None)
         with pytest.raises(ConfigurationError):
             Client(api_key="   ")