diff --git a/openerp/addons/base/res/res_users.py b/openerp/addons/base/res/res_users.py
index 43e5a34c02b..0a2d8339ac5 100644
--- a/openerp/addons/base/res/res_users.py
+++ b/openerp/addons/base/res/res_users.py
@@ -31,6 +31,7 @@ import openerp
 from openerp import SUPERUSER_ID, models
 from openerp import tools
 import openerp.exceptions
+from openerp import api
 from openerp.osv import fields, osv, expression
 from openerp.service.security import check_super
 from openerp.tools.translate import _
@@ -548,8 +549,19 @@ class res_users(osv.osv):
             'target': 'new',
         }
 
-    @tools.ormcache(skiparg=2)
+    @api.v7
     def has_group(self, cr, uid, group_ext_id):
+        return self._has_group(cr, uid, group_ext_id)
+    @api.v8
+    def has_group(self, group_ext_id):
+        # use singleton's id if called on a non-empty recordset, otherwise
+        # context uid
+        uid = self.id if self else self.env.uid
+        return self._has_group(self.env.cr, uid, group_ext_id)
+
+    @api.noguess
+    @tools.ormcache(skiparg=2)
+    def _has_group(self, cr, uid, group_ext_id):
         """Checks whether user belongs to given group.
 
         :param str group_ext_id: external ID (XML ID) of the group.
@@ -564,6 +576,8 @@ class res_users(osv.osv):
                         (SELECT res_id FROM ir_model_data WHERE module=%s AND name=%s)""",
                    (uid, module, ext_id))
         return bool(cr.fetchone())
+    # for a few places explicitly clearing the has_group cache
+    has_group.clear_cache = _has_group.clear_cache
 
 #----------------------------------------------------------
 # Implied groups
diff --git a/openerp/addons/base/tests/__init__.py b/openerp/addons/base/tests/__init__.py
index c597542d052..e6441d42aae 100644
--- a/openerp/addons/base/tests/__init__.py
+++ b/openerp/addons/base/tests/__init__.py
@@ -20,6 +20,7 @@ import test_res_lang
 import test_search
 import test_translate
 #import test_uninstall
+import test_user_has_group
 import test_view_validation
 import test_views
 import test_xmlrpc
diff --git a/openerp/addons/base/tests/test_user_has_group.py b/openerp/addons/base/tests/test_user_has_group.py
new file mode 100644
index 00000000000..e13d04f5f6f
--- /dev/null
+++ b/openerp/addons/base/tests/test_user_has_group.py
@@ -0,0 +1,49 @@
+# -*- coding: utf-8 -*-
+import openerp.tests
+
+class TestHasGroup(openerp.tests.TransactionCase):
+    def setUp(self):
+        super(TestHasGroup, self).setUp()
+
+        group0 = self.env['ir.model.data']._update(
+            'res.groups', 'test_user_has_group',
+            {'name': 'group0'},
+            xml_id='group0'
+        )
+        self.group0 = 'test_user_has_group.group0'
+        self.env['ir.model.data']._update(
+            'res.groups', 'test_user_has_group',
+            {'name': 'group1'},
+            xml_id='group1'
+        )
+        self.group1 = 'test_user_has_group.group1'
+
+        self.test_user = self.env['res.users'].create({
+            'login': 'testuser',
+            'partner_id': self.env['res.partner'].create({
+                'name': "Strawman Test User"
+            }).id,
+            'groups_id': [(4, group0, 0)]
+        })
+
+    def test_old_api(self):
+        Users = self.registry['res.users']
+
+        self.assertTrue(
+            Users.has_group(self.cr, self.test_user.id, self.group0),
+            "the test user should belong to group0"
+        )
+        self.assertFalse(
+            Users.has_group(self.cr, self.test_user.id, self.group1),
+            "the test user should *not* belong to group1"
+        )
+
+    def test_new_api(self):
+        self.assertTrue(
+            self.test_user.has_group(self.group0),
+            "the test user should belong to group0",
+        )
+        self.assertFalse(
+            self.test_user.has_group(self.group1),
+            "the test user shoudl not belong to group1"
+        )