diff --git a/miio/devicestatus.py b/miio/devicestatus.py
index 66f605f4d..f38c3d9b5 100644
--- a/miio/devicestatus.py
+++ b/miio/devicestatus.py
@@ -131,7 +131,7 @@ def __getattr__(self, item):
         return getattr(self._embedded[embed], prop)
 
 
-def sensor(name: str, *, unit: str = "", **kwargs):
+def sensor(name: str, *, unit: Optional[str] = None, **kwargs):
     """Syntactic sugar to create SensorDescriptor objects.
 
     The information can be used by users of the library to programmatically find out what