diff --git a/membershipworks/models.py b/membershipworks/models.py
index d03816d..70c2b5e 100644
--- a/membershipworks/models.py
+++ b/membershipworks/models.py
@@ -563,6 +563,7 @@ class EventExt(Event):
             return self.instructor.member == member
         return False
 
+    @property
     def ready_for_invoice(self) -> bool:
         return (
             self.instructor is not None