diff --git a/openevsehttp/__init__.py b/openevsehttp/__init__.py
index 8d3f2f3..4afd20e 100644
--- a/openevsehttp/__init__.py
+++ b/openevsehttp/__init__.py
@@ -446,7 +446,10 @@ async def set_current(self, amps: int = 6) -> None:
         """Set the soft current limit."""
         url = f"{self.url}config"
 
-        if amps < self._config["min_current_hard"] or amps > self._config["max_current_hard"]:
+        if (
+            amps < self._config["min_current_hard"]
+            or amps > self._config["max_current_hard"]
+        ):
             _LOGGER.error("Invalid value for max_current_soft: %s", amps)
             raise ValueError
 
@@ -458,8 +461,7 @@ async def set_current(self, amps: int = 6) -> None:
         )  # noqa: E501
         if response["msg"] != "done":
             _LOGGER.error("Problem issuing command: %s", response["msg"])
-            raise UnknownError        
-
+            raise UnknownError
 
     @property
     def hostname(self) -> str:
@@ -746,7 +748,7 @@ def divert_active(self) -> bool:
         return self._status["divert_active"]
 
     @property
-    def wifi_serial(self) -> str:
+    def wifi_serial(self) -> str | None:
         """Return wifi serial."""
         if self._config is not None and "wifi_serial" in self._config:
             return self._config["wifi_serial"]
diff --git a/tests/test_init.py b/tests/test_init.py
index 7fd380c..ac06cb9 100644
--- a/tests/test_init.py
+++ b/tests/test_init.py
@@ -612,6 +612,7 @@ async def test_toggle_override_v2(test_charger_v2, mock_aioclient, caplog):
         await test_charger_v2.toggle_override()
     assert "Toggling manual override via RAPI" in caplog.text
 
+
 @pytest.mark.parametrize(
     "fixture, expected", [("test_charger", "1234567890AB"), ("test_charger_v2", None)]
 )
@@ -622,6 +623,7 @@ async def test_wifi_serial(fixture, expected, request):
     status = charger.wifi_serial
     assert status == expected
 
+
 async def test_set_current(test_charger, mock_aioclient, caplog):
     """Test v4 Status reply"""
     await test_charger.update()
@@ -633,7 +635,8 @@ async def test_set_current(test_charger, mock_aioclient, caplog):
     )
     with caplog.at_level(logging.DEBUG):
         await test_charger.set_current(12)
-    assert "Setting max_current_soft to 12" in caplog.text    
+    assert "Setting max_current_soft to 12" in caplog.text
+
 
 async def test_set_current_error(test_charger, mock_aioclient, caplog):
     """Test v4 Status reply"""
@@ -646,4 +649,4 @@ async def test_set_current_error(test_charger, mock_aioclient, caplog):
     with caplog.at_level(logging.DEBUG):
         with pytest.raises(ValueError):
             await test_charger.set_current(60)
-    assert "Invalid value for max_current_soft: 60" in caplog.text        
\ No newline at end of file
+    assert "Invalid value for max_current_soft: 60" in caplog.text