diff --git a/charge_control.py b/charge_control.py
index 0aeae28..4ded7f2 100644
--- a/charge_control.py
+++ b/charge_control.py
@@ -123,7 +123,7 @@ class ChargeControls(dict):
         config_str = json.dumps(chd, sort_keys=True, indent=4).encode('utf-8')
         new_hash = md5(config_str).hexdigest()
         if force or self._config_hash != new_hash:
-            with open(self.file_name, "wb", encoding="utf-8") as f:
+            with open(self.file_name, "wb") as f:
                 f.write(config_str)
             self._config_hash = new_hash
             logger.info("save config change")