diff --git a/addons/event_sale/models/event_registration.py b/addons/event_sale/models/event_registration.py
index 26a6a64802b..e765e016035 100644
--- a/addons/event_sale/models/event_registration.py
+++ b/addons/event_sale/models/event_registration.py
@@ -105,7 +105,8 @@ class EventRegistration(models.Model):
     def _synchronize_so_line_values(self, so_line):
         if so_line:
             return {
-                'partner_id': False if self.env.user._is_public() else so_line.order_id.partner_id.id,
+                # Avoid registering public users but respect the portal workflows
+                'partner_id': False if self.env.user._is_public() and self.env.user.partner_id == so_line.order_id.partner_id else so_line.order_id.partner_id.id,
                 'event_id': so_line.event_id.id,
                 'event_ticket_id': so_line.event_ticket_id.id,
                 'sale_order_id': so_line.order_id.id,