diff --git a/app/scodoc/sco_groups.py b/app/scodoc/sco_groups.py
index 689dab34..ab3e014d 100644
--- a/app/scodoc/sco_groups.py
+++ b/app/scodoc/sco_groups.py
@@ -745,7 +745,7 @@ def setGroups(
         except ValueError:
             log(f"setGroups: ignoring invalid group_id={group_id}")
             continue
-        group: GroupDescr = GroupDescr.query.get(group_id)
+        group: GroupDescr = GroupDescr.query.get_or_404(group_id)
         # Anciens membres du groupe:
         old_members_set = {etud.id for etud in group.etuds}
         # Place dans ce groupe les etudiants indiqués: