diff --git a/src/model.js b/src/model.js
index 7d3a2bb7f3..5441a88330 100644
--- a/src/model.js
+++ b/src/model.js
@@ -794,7 +794,8 @@
                 }
                 var field = this.model.fields[name];
                 if (field.description.readonly &&
-                        !(field instanceof Sao.field.One2Many)) {
+                        !((field instanceof Sao.field.One2Many) &&
+                            !(field instanceof Sao.field.Many2Many))) {
                     continue;
                 }
                 if ((this._changed[name] === undefined) && this.id >= 0) {