diff --git a/aleksis/core/mixins.py b/aleksis/core/mixins.py
index d2c8fc0539293eda74713fea0d84287851c940aa..2d06ba0dc84bf79edf74cbdbbb25b7d50da33da0 100644
--- a/aleksis/core/mixins.py
+++ b/aleksis/core/mixins.py
@@ -154,8 +154,6 @@ class ExtensibleModel(models.Model, metaclass=_ExtensibleModelBase):
 
     extended_data = JSONField(default=dict, editable=False)
 
-    extended_data = JSONField(default=dict, editable=False)
-
     @classmethod
     def _safe_add(cls, obj: Any, name: Optional[str]) -> None:
         # Decide the name for the attribute