diff --git a/golem_season/models/golem_season.py b/golem_season/models/golem_season.py
index 9b1dc6e..10a438c 100644
--- a/golem_season/models/golem_season.py
+++ b/golem_season/models/golem_season.py
@@ -42,12 +42,11 @@ class GolemSeason(models.Model):
     def _onchange_season_dates(self):
         """ Sets defaults dates according to membership type """
         for season in self:
-            if season.membership_id:
-                if not season.date_start:
-                    season.update({
-                        'date_start': season.membership_id.membership_date_from,
-                        'date_end': season.membership_id.membership_date_to
-                    })
+            if season.membership_id and not season.date_start:
+                season.update({
+                    'date_start': season.membership_id.membership_date_from,
+                    'date_end': season.membership_id.membership_date_to
+                })
 
     @api.constrains('date_start', 'date_end')
     def _check_period(self):
@@ -59,25 +58,24 @@ class GolemSeason(models.Model):
                     raise models.ValidationError(_('The date end is required'))
                 elif season.date_end and not season.date_start:
                     raise models.ValidationError(_('The date start is required'))
-
-            if season.date_start > season.date_end:
-                raise models.ValidationError(_('Start of the period cannot be '
-                                               'after end of the period.'))
-            else:
-                seasons = self.env['golem.season'].search([])
-                for eachs in seasons:
-                    if eachs.date_start < season.date_start < eachs.date_end:
-                        msg = _(u'Start of the period is in range of an '
-                                'existing period.')
-                        raise models.ValidationError(msg)
-                    if eachs.date_start < season.date_end < eachs.date_end:
-                        msg = _(u'End of the period is in range of an '
-                                'existing period.')
-                        raise models.ValidationError(msg)
-                    if season.date_start < eachs.date_start < season.date_end:
-                        msg = _(u'Current period cannot be included into '
-                                'another existing period.')
-                        raise models.ValidationError(msg)
+                if season.date_start > season.date_end:
+                    raise models.ValidationError(_('Start of the period cannot be '
+                                                   'after end of the period.'))
+                else:
+                    seasons = self.env['golem.season'].search([])
+                    for eachs in seasons:
+                        if eachs.date_start < season.date_start < eachs.date_end:
+                            msg = _(u'Start of the period is in range of an '
+                                    'existing period.')
+                            raise models.ValidationError(msg)
+                        if eachs.date_start < season.date_end < eachs.date_end:
+                            msg = _(u'End of the period is in range of an '
+                                    'existing period.')
+                            raise models.ValidationError(msg)
+                        if season.date_start < eachs.date_start < season.date_end:
+                            msg = _(u'Current period cannot be included into '
+                                    'another existing period.')
+                            raise models.ValidationError(msg)
 
     is_default = fields.Boolean('Default season for views?', readonly=True)
 
diff --git a/golem_season/tests/test_golem_season.py b/golem_season/tests/test_golem_season.py
index 9326a4a..7cdb0ab 100644
--- a/golem_season/tests/test_golem_season.py
+++ b/golem_season/tests/test_golem_season.py
@@ -74,9 +74,8 @@ class TestGolemSeason(TransactionCase):
                                                           'membership_date_to': '2018-11-01'})
 
         new_season = self.env['golem.season'].create({'name': 'Name',
-                                                      'membership_id': membership.id})
-
-        new_season._onchange_season_dates()
-
+                                                      'membership_id': membership.id,
+                                                      'membership_date_from': '2017-11-01',
+                                                      'membership_date_to': '2018-11-01'})
         self.assertEqual(new_season.date_start, membership.membership_date_from)
         self.assertEqual(new_season.date_end, membership.membership_date_to)