diff --git a/sao/src/view/form.js b/sao/src/view/form.js
index 3d62d718a0..87db9aff98 100644
--- a/sao/src/view/form.js
+++ b/sao/src/view/form.js
@@ -5337,7 +5337,7 @@ function eval_pyson(value){
 
             var value = field.get_client(record);
             var new_key_names = Object.keys(value).filter(
-                e => !this.fields[e]);
+                e => !this.field.keys[e]);
 
             var prm;
             if (!jQuery.isEmptyObject(new_key_names)) {