# UNDF: UNDF-2026-000000897
--- a/trytond/trytond/model/modelview.py
+++ b/trytond/trytond/model/modelview.py
@@ -922,7 +922,7 @@
                     init_targets = getattr(init_record, fname, [])
                 value = collections.defaultdict(list)
-                previous = [t.id for t in init_targets if t.id]
+                previous = set(t.id for t in init_targets if t.id)
                 for i, target in enumerate(targets):
                     if (field._type == 'one2many'
                             and field.field
@@ -936,7 +936,7 @@
                     try:
                         if target.id in previous:
-                            previous.remove(target.id)
+                            previous.discard(target.id)
                             if isinstance(target, ModelView):
                                 target_changed = target._changed_values()
                                 if target_changed: