diff --git a/openerp/addons/base/res/res_users.py b/openerp/addons/base/res/res_users.py
index 523db591a73..60b19502fd0 100644
--- a/openerp/addons/base/res/res_users.py
+++ b/openerp/addons/base/res/res_users.py
@@ -162,6 +162,12 @@ class res_users(osv.osv):
             res[user.id] = not self.has_group(cr, user.id, 'base.group_user')
         return res
 
+    def _store_trigger_share_res_groups(self, cr, uid, ids, context=None):
+        group_user = self.pool['ir.model.data'].xmlid_to_object(cr, SUPERUSER_ID, 'base.group_user', context=context)
+        if group_user and group_user.id in ids:
+            return group_user.users.ids
+        return []
+
     def _get_users_from_group(self, cr, uid, ids, context=None):
         result = set()
         groups = self.pool['res.groups'].browse(cr, uid, ids, context=context)
@@ -197,8 +203,8 @@ class res_users(osv.osv):
         'company_ids':fields.many2many('res.company','res_company_users_rel','user_id','cid','Companies'),
         'share': fields.function(_is_share, string='Share User', type='boolean',
              store={
-                 'res.users': (lambda self, cr, uid, ids, c={}: ids, None, 50),
-                 'res.groups': (_get_users_from_group, None, 50),
+                 'res.users': (lambda self, cr, uid, ids, c={}: ids, ['groups_id'], 50),
+                 'res.groups': (_store_trigger_share_res_groups, ['users'], 50),
              }, help="External user with limited access, created only for the purpose of sharing data."),
     }
 
diff --git a/openerp/addons/base/security/base_security.xml b/openerp/addons/base/security/base_security.xml
index a93dd785e26..c5c60632758 100644
--- a/openerp/addons/base/security/base_security.xml
+++ b/openerp/addons/base/security/base_security.xml
@@ -23,7 +23,6 @@
 
         <record model="res.groups" id="group_user">
             <field name="name">Employee</field>
-            <field name="users" eval="[(4, ref('base.user_root'))]"/>
         </record>
 
         <record model="res.groups" id="group_light_multi_company">
@@ -44,6 +43,7 @@
         </record>
         <record model="res.groups" id="group_user">
             <field name="implied_ids" eval="[(4, ref('group_no_one'))]"/>
+            <field name="users" eval="[(4, ref('base.user_root'))]"/>
         </record>
 
         <record id="group_sale_salesman" model="res.groups">
diff --git a/openerp/addons/base/tests/test_orm.py b/openerp/addons/base/tests/test_orm.py
index a288a1c2f37..9f96931ad44 100644
--- a/openerp/addons/base/tests/test_orm.py
+++ b/openerp/addons/base/tests/test_orm.py
@@ -166,6 +166,22 @@ class TestORM(common.TransactionCase):
                         ['date'], ['date:month', 'date:day'], lazy=False)
         self.assertEqual(len(rg), len(all_partners))
 
+    def test_m2m_store_trigger(self):
+        group_user = self.env.ref('base.group_user')
+
+        user = self.env['res.users'].create({
+            'name': 'test',
+            'login': 'test_m2m_store_trigger',
+            'groups_id': [(6, 0, [])],
+        })
+        self.assertTrue(user.share)
+
+        group_user.write({'users': [(4, user.id)]})
+        self.assertFalse(user.share)
+
+        group_user.write({'users': [(3, user.id)]})
+        self.assertTrue(user.share)
+
 
 class TestInherits(common.TransactionCase):
     """ test the behavior of the orm for models that use _inherits;