diff --git a/golem_activity/models/golem_activity.py b/golem_activity/models/golem_activity.py
index f95db0b..472ecc2 100644
--- a/golem_activity/models/golem_activity.py
+++ b/golem_activity/models/golem_activity.py
@@ -47,7 +47,8 @@ class GolemActivity(models.Model):
         return self.env['golem.season'].search(domain)
 
     season_id = fields.Many2one('golem.season', string='Season', copy=False,
-                                required=True, default=_default_season)
+                                required=True, default=_default_season,
+                                ondelete='restrict')
     animator_id = fields.Many2one('res.partner', string='Animator',
                                   domain=[('is_company', '=', False)])
     date_start = fields.Date('Start date', copy=False)
diff --git a/golem_member/models/golem_member.py b/golem_member/models/golem_member.py
index f8fc7c2..47a7bae 100644
--- a/golem_member/models/golem_member.py
+++ b/golem_member/models/golem_member.py
@@ -67,7 +67,8 @@ class GolemMember(models.Model):
     opt_out_sms = fields.Boolean('Out of SMS campaigns')
     season_ids = fields.Many2many('golem.season', string='Seasons',
                                   required=True, auto_join=True,
-                                  default=_default_season)
+                                  default=_default_season,
+                                  ondelete='restrict')
     is_current = fields.Boolean('Current user?', default=False, readonly=True,
                                 store=True, compute='_compute_is_current')
     is_number_manual = fields.Boolean('Is number manual?', store=False,