diff --git a/CHANGELOG b/CHANGELOG
index 050135ff10..cc00f17975 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,4 @@
+* Remove order constraint on register ModelSQL
 * Add relate from report to translations
 
 Version 4.2.0 - 2016-11-28
diff --git a/trytond/model/modelsql.py b/trytond/model/modelsql.py
index 3d5d16496a..9b7e3b7352 100644
--- a/trytond/model/modelsql.py
+++ b/trytond/model/modelsql.py
@@ -188,7 +188,11 @@ class ModelSQL(ModelStorage):
                 if field.model_name in ('res.user', 'res.group'):
                     ref = field.model_name.replace('.', '_')
                 else:
-                    ref = pool.get(field.model_name)._table
+                    ref_model = pool.get(field.model_name)
+                    ref = ref_model._table
+                    # Create foreign key table if missing
+                    if not TableHandler.table_exist(ref):
+                        TableHandler(ref_model)
                 if field_name in ['create_uid', 'write_uid']:
                     # migration from 3.6
                     table.drop_fk(field_name)
diff --git a/trytond/res/__init__.py b/trytond/res/__init__.py
index d80ac99b99..582d34c17d 100644
--- a/trytond/res/__init__.py
+++ b/trytond/res/__init__.py
@@ -15,7 +15,6 @@ def register():
         Group,
         User,
         LoginAttempt,
-        Group2,
         UserAction,
         UserGroup,
         Warning_,
diff --git a/trytond/res/group.py b/trytond/res/group.py
index 528e5fcc27..b87a712091 100644
--- a/trytond/res/group.py
+++ b/trytond/res/group.py
@@ -3,12 +3,10 @@
 "Group"
 from itertools import chain
 from ..model import ModelView, ModelSQL, fields, Unique
-from ..pool import Pool, PoolMeta
+from ..pool import Pool
 from ..tools import grouped_slice
 
-__all__ = [
-    'Group', 'Group2',
-    ]
+__all__ = ['Group']
 
 
 class MenuMany2Many(fields.Many2Many):
@@ -33,6 +31,7 @@ class Group(ModelSQL, ModelView):
     "Group"
     __name__ = "res.group"
     name = fields.Char('Name', required=True, select=True, translate=True)
+    users = fields.Many2Many('res.user-res.group', 'group', 'user', 'Users')
     model_access = fields.One2Many('ir.model.access', 'group',
        'Access Model')
     field_access = fields.One2Many('ir.model.field.access', 'group',
@@ -115,9 +114,3 @@ class Group(ModelSQL, ModelView):
         pool.get('ir.model.access')._get_access_cache.clear()
         pool.get('ir.model.field.access')._get_access_cache.clear()
         ModelView._fields_view_get_cache.clear()
-
-
-class Group2:
-    __metaclass__ = PoolMeta
-    __name__ = "res.group"
-    users = fields.Many2Many('res.user-res.group', 'group', 'user', 'Users')