diff --git a/participation/models.py b/participation/models.py
index f6ece2d..7462010 100644
--- a/participation/models.py
+++ b/participation/models.py
@@ -237,7 +237,7 @@ class Team(models.Model):
         get_sympa_client().delete_list(f"equipe-{self.trigram}")
 
     def clean(self):
-        if len(self.trigram) != settings.TEAM_CODE_LENGTH:
+        if self.trigram and len(self.trigram) != settings.TEAM_CODE_LENGTH:
             raise ValidationError({'trigram': _("The team code must be composed of {nb_letters} uppercase letters.")},
                                   params={'nb_letters': settings.TEAM_CODE_LENGTH})
         return super().clean()