diff --git a/trytond/osv/orm.py b/trytond/osv/orm.py
index ce622cdad2..077674b355 100644
--- a/trytond/osv/orm.py
+++ b/trytond/osv/orm.py
@@ -669,53 +669,53 @@ class ORM(object):
                                 cursor.execute("DROP INDEX \"%s_%s_index\"" % \
                                         (self._table, k))
                             if isinstance(field, fields.Many2One):
-                                ref_obj = self.pool.get(field._obj)
-                                if ref_obj:
-                                    ref = ref_obj._table
+                                # for some fields in ir are linked to res objects
+                                # that are not yet in the pooler
+                                if field._obj in ('res.user', 'res.group'):
+                                    ref = field._obj.replace('.','_')
                                 else:
-                                    ref = field._obj.replace('.', '_')
-                                if ref != 'ir_actions':
-                                    cursor.execute('SELECT confdeltype, conname ' \
-                                            'FROM pg_constraint as con, ' \
-                                                'pg_class as cl1, pg_class as cl2, ' \
-                                            'pg_attribute as att1, pg_attribute as att2 ' \
-                                            'WHERE con.conrelid = cl1.oid ' \
-                                                'AND cl1.relname = %s ' \
-                                                'AND con.confrelid = cl2.oid ' \
-                                                'AND cl2.relname = %s ' \
-                                                'AND array_lower(con.conkey, 1) = 1 ' \
-                                                'AND con.conkey[1] = att1.attnum ' \
-                                                'AND att1.attrelid = cl1.oid ' \
-                                                'AND att1.attname = %s ' \
-                                                'AND array_lower(con.confkey, 1) = 1 ' \
-                                                'AND con.confkey[1] = att2.attnum ' \
-                                                'AND att2.attrelid = cl2.oid ' \
-                                                'AND att2.attname = %s ' \
-                                                'AND con.contype = \'f\'',
-                                            (self._table, ref, k, 'id'))
-                                    res = cursor.dictfetchall()
-                                    if res:
-                                        confdeltype = {
-                                                'RESTRICT': 'r',
-                                                'NO ACTION': 'a',
-                                                'CASCADE': 'c',
-                                                'SET NULL': 'n',
-                                                'SET DEFAULT': 'd',
-                                        }
-                                        if res[0]['confdeltype'] != \
-                                                confdeltype.get(
-                                                        field.ondelete.upper(),
-                                                        'a'):
-                                            cursor.execute('ALTER TABLE "' + \
-                                                    self._table + '" ' \
-                                                    'DROP CONSTRAINT "' + \
-                                                    res[0]['conname'] + '"')
-                                            cursor.execute('ALTER TABLE "' + \
-                                                    self._table + '" ' \
-                                                    'ADD FOREIGN KEY ' \
-                                                    '("' + k + '") ' \
-                                                    'REFERENCES "' + ref + \
-                                                    '" ON DELETE ' + field.ondelete)
+                                    ref = self.pool.get(field._obj)._table
+                                cursor.execute('SELECT confdeltype, conname ' \
+                                        'FROM pg_constraint as con, ' \
+                                            'pg_class as cl1, pg_class as cl2, ' \
+                                        'pg_attribute as att1, pg_attribute as att2 ' \
+                                        'WHERE con.conrelid = cl1.oid ' \
+                                            'AND cl1.relname = %s ' \
+                                            'AND con.confrelid = cl2.oid ' \
+                                            'AND cl2.relname = %s ' \
+                                            'AND array_lower(con.conkey, 1) = 1 ' \
+                                            'AND con.conkey[1] = att1.attnum ' \
+                                            'AND att1.attrelid = cl1.oid ' \
+                                            'AND att1.attname = %s ' \
+                                            'AND array_lower(con.confkey, 1) = 1 ' \
+                                            'AND con.confkey[1] = att2.attnum ' \
+                                            'AND att2.attrelid = cl2.oid ' \
+                                            'AND att2.attname = %s ' \
+                                            'AND con.contype = \'f\'',
+                                        (self._table, ref, k, 'id'))
+                                res = cursor.dictfetchall()
+                                if res:
+                                    confdeltype = {
+                                            'RESTRICT': 'r',
+                                            'NO ACTION': 'a',
+                                            'CASCADE': 'c',
+                                            'SET NULL': 'n',
+                                            'SET DEFAULT': 'd',
+                                    }
+                                    if res[0]['confdeltype'] != \
+                                            confdeltype.get(
+                                                    field.ondelete.upper(),
+                                                    'a'):
+                                        cursor.execute('ALTER TABLE "' + \
+                                                self._table + '" ' \
+                                                'DROP CONSTRAINT "' + \
+                                                res[0]['conname'] + '"')
+                                        cursor.execute('ALTER TABLE "' + \
+                                                self._table + '" ' \
+                                                'ADD FOREIGN KEY ' \
+                                                '("' + k + '") ' \
+                                                'REFERENCES "' + ref + \
+                                                '" ON DELETE ' + field.ondelete)
                     else:
                         # TODO add error message
                         logger.notify_channel('init', LOG_ERROR, '')