diff --git a/src/bonsai/bonsai/bim/operator.py b/src/bonsai/bonsai/bim/operator.py
index f769179934..578f065b17 100644
--- a/src/bonsai/bonsai/bim/operator.py
+++ b/src/bonsai/bonsai/bim/operator.py
@@ -1437,6 +1437,11 @@ class BIM_OT_attribute_add_subitem(bpy.types.Operator):
     def execute(self, context) -> set["rna_enums.OperatorReturnItems"]:
         col: bpy.types.bpy_prop_collection_idprop[StrProperty]
         col = eval(self.data_path)
+
+        attr: "Attribute" = col.data
+        if attr.is_optional and not col:
+            attr.is_null = False
+
         col.add()
         return {"FINISHED"}
 
@@ -1459,4 +1464,9 @@ class BIM_OT_attribute_remove_subitem(bpy.types.Operator):
         col: bpy.types.bpy_prop_collection_idprop[StrProperty]
         col = eval(self.data_path)
         col.remove(self.index)
+
+        attr: "Attribute" = col.data
+        if attr.is_optional and not col:
+            attr.is_null = True
+
         return {"FINISHED"}