diff --git a/custom_components/ocpp/api.py b/custom_components/ocpp/api.py
index 359383e3..4f8426de 100644
--- a/custom_components/ocpp/api.py
+++ b/custom_components/ocpp/api.py
@@ -138,7 +138,7 @@ async def create(hass: HomeAssistant, entry: ConfigEntry):
             self.on_connect,
             self.host,
             self.port,
-            subprotocols=self.subprotocol,
+            subprotocols=[self.subprotocol],
             ping_timeout=None,
             close_timeout=10,
         )