diff --git a/tests/components/light/test_tradfri.py b/tests/components/light/test_tradfri.py
index 8ef5d17452a..12c596f3f09 100644
--- a/tests/components/light/test_tradfri.py
+++ b/tests/components/light/test_tradfri.py
@@ -229,6 +229,7 @@ async def setup_gateway(hass, mock_gateway, mock_api,
             patch('pytradfri.api.aiocoap_api.APIFactory.request', mock_api), \
             patch('pytradfri.Gateway', return_value=mock_gateway), \
             patch.object(tradfri, 'load_json', return_value=known_hosts), \
+            patch.object(tradfri, 'save_json'), \
             patch.object(hass.components.configurator, 'request_config',
                          request_config):