diff -r 18cabfbc7ac2 trytond/model/modelview.py
--- a/trytond/trytond/model/modelview.py	Mon Jun 05 23:36:11 2017 +0200
+++ b/trytond/trytond/model/modelview.py	Mon Jun 19 12:13:17 2017 +0200
@@ -720,7 +720,15 @@
                             target_changed['id'] = target.id
                             value['update'].append(target_changed)
                     else:
-                        value['add'].append((i, target._default_values))
+                        # Ensure initial values are returned because target was
+                        # instantiated on server side.
+                        target_init_values = target._init_values
+                        target._init_values = None
+                        try:
+                            value['add'].append((i, target._changed_values))
+                        finally:
+                            target._init_values = target_init_values
+
                 if not value['remove']:
                     del value['remove']
                 if not value: