diff --git a/app/scodoc/sco_edit_ue.py b/app/scodoc/sco_edit_ue.py
index d581bb658e..1ce7c347aa 100644
--- a/app/scodoc/sco_edit_ue.py
+++ b/app/scodoc/sco_edit_ue.py
@@ -653,6 +653,12 @@ def ue_table(formation_id=None, semestre_idx=1, msg=""):  # was ue_list
     ues_obj = UniteEns.query.filter_by(
         formation_id=formation_id, is_external=False
     ).order_by(UniteEns.semestre_idx, UniteEns.numero)
+    # safety check: renumérote les ue s'il en manque ou s'il y a des ex-aequo.
+    # cela facilite le travail de la passerelle !
+    numeros = {ue.numero for ue in ues_obj}
+    if (None in numeros) or len(numeros) < ues_obj.count():
+        scu.objects_renumber(db, ues_obj)
+
     ues_externes_obj = UniteEns.query.filter_by(
         formation_id=formation_id, is_external=True
     )