diff --git a/sao/src/model.js b/sao/src/model.js
index c8e7546fd2..d9f3a09b6f 100644
--- a/sao/src/model.js
+++ b/sao/src/model.js
@@ -2379,6 +2379,7 @@
             }
 
             if (value && (value.add || value.update)) {
+                let vals_to_set = {};
                 // First set already added fields to prevent triggering a
                 // second on_change call
                 if (value.update) {
@@ -2388,9 +2389,9 @@
                         }
                         var record2 = group.get(vals.id);
                         if (record2) {
-                            var vals_to_set = {};
                             for (var key in vals) {
-                                if (!Object.prototype.hasOwnProperty.call(new_field_names, key)) {
+                                if (!Object.prototype.hasOwnProperty.call(
+                                    new_field_names, key)) {
                                     vals_to_set[key] = vals[key];
                                 }
                             }
@@ -2426,7 +2427,10 @@
                         if (record2) {
                             let to_update = Object.fromEntries(
                                 Object.entries(vals).filter(
-                                    ([k, v]) => !Object.prototype.hasOwnProperty.call(vals_to_set, k)
+                                    ([k, v]) => {
+                                        !Object.prototype.hasOwnProperty.call(
+                                            vals_to_set, k)
+                                    }
                                 ));
                             record2.set_on_change(to_update);
                         }
diff --git a/tryton/tryton/gui/window/view_form/model/field.py b/tryton/tryton/gui/window/view_form/model/field.py
index a434bd1cd1..8fab0561d3 100644
--- a/tryton/tryton/gui/window/view_form/model/field.py
+++ b/tryton/tryton/gui/window/view_form/model/field.py
@@ -798,6 +798,7 @@ class O2MField(Field):
                         force_remove=False)
 
         if value and (value.get('add') or value.get('update', [])):
+            vals_to_set = {}
             # First set already added fields to prevent triggering a
             # second on_change call
             for vals in value.get('update', []):