diff --git a/homeassistant/components/upnp/entity.py b/homeassistant/components/upnp/entity.py
index e53d89018fb..add8039345b 100644
--- a/homeassistant/components/upnp/entity.py
+++ b/homeassistant/components/upnp/entity.py
@@ -19,7 +19,7 @@ class UpnpEntityDescription(EntityDescription):
 
     def __post_init__(self):
         """Post initialize."""
-        self.value_key = self.value_key or self.key
+        object.__setattr__(self, "value_key", self.value_key or self.key)
 
 
 class UpnpEntity(CoordinatorEntity[UpnpDataUpdateCoordinator]):