diff --git a/custom_components/mylight_systems/coordinator.py b/custom_components/mylight_systems/coordinator.py
index 07a7709..4090a46 100644
--- a/custom_components/mylight_systems/coordinator.py
+++ b/custom_components/mylight_systems/coordinator.py
@@ -43,7 +43,7 @@ class MyLightSystemsCoordinatorData(NamedTuple):
     msb_discharge: Measure
     green_energy: Measure
     battery_state: Measure
-    master_relay_state: str
+    master_relay_state: str | None
 
 
 # https://developers.home-assistant.io/docs/integration_fetching_data#coordinated-single-api-poll-for-data-for-all-entities
diff --git a/custom_components/mylight_systems/switch.py b/custom_components/mylight_systems/switch.py
index a00ee09..c3d2df6 100644
--- a/custom_components/mylight_systems/switch.py
+++ b/custom_components/mylight_systems/switch.py
@@ -38,7 +38,7 @@ async def async_setup_entry(hass: HomeAssistant, entry: ConfigEntry, async_add_e
 
     switches: list[MyLightSystemsSwitchEntityDescription] = []
 
-    if entry.data[CONF_MASTER_RELAY_ID] is not None:
+    if entry.data.get(CONF_MASTER_RELAY_ID, None) is not None:
         switches.append(master_relay_switch)
 
     async_add_entities(