diff --git a/greendeck/lib/homeassistant/__init__.py b/greendeck/lib/homeassistant/__init__.py
index 584e23c..6c014f9 100644
--- a/greendeck/lib/homeassistant/__init__.py
+++ b/greendeck/lib/homeassistant/__init__.py
@@ -101,7 +101,7 @@ class EventState(BaseModel):
 class EventData(BaseModel):
     entity_id: str
     new_state: EventState
-    old_state: EventState
+    old_state: EventState | None
 
 
 class Event(BaseModel):