diff --git a/custom_components/ocpp/api.py b/custom_components/ocpp/api.py
index f1f058cc..eeefba2f 100644
--- a/custom_components/ocpp/api.py
+++ b/custom_components/ocpp/api.py
@@ -5,6 +5,7 @@
 import logging
 import ssl
 
+from functools import partial
 from homeassistant.config_entries import ConfigEntry
 from homeassistant.const import STATE_OK
 from homeassistant.core import HomeAssistant
@@ -90,26 +91,31 @@ def __init__(self, hass: HomeAssistant, entry: ConfigEntry):
         self.config = entry.data
         self.id = entry.entry_id
         self.charge_points = {}
-        if entry.data.get(CONF_SSL, DEFAULT_SSL):
+
+    @staticmethod
+    async def create(hass: HomeAssistant, entry: ConfigEntry):
+        """Create instance and start listening for OCPP connections on given port."""
+        self = CentralSystem(hass, entry)
+
+        if self.entry.data.get(CONF_SSL, DEFAULT_SSL):
             self.ssl_context = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
             # see https://community.home-assistant.io/t/certificate-authority-and-self-signed-certificate-for-ssl-tls/196970
-            localhost_certfile = entry.data.get(
+            localhost_certfile = self.entry.data.get(
                 CONF_SSL_CERTFILE_PATH, DEFAULT_SSL_CERTFILE_PATH
             )
-            localhost_keyfile = entry.data.get(
+            localhost_keyfile = self.entry.data.get(
                 CONF_SSL_KEYFILE_PATH, DEFAULT_SSL_KEYFILE_PATH
             )
-            self.ssl_context.load_cert_chain(
-                localhost_certfile, keyfile=localhost_keyfile
+            await self.hass.async_add_executor_job(
+                partial(
+                    self.ssl_context.load_cert_chain,
+                    localhost_certfile,
+                    keyfile=localhost_keyfile,
+                )
             )
         else:
             self.ssl_context = None
 
-    @staticmethod
-    async def create(hass: HomeAssistant, entry: ConfigEntry):
-        """Create instance and start listening for OCPP connections on given port."""
-        self = CentralSystem(hass, entry)
-
         server = await websockets.serve(
             self.on_connect,
             self.host,