diff --git a/app/scodoc/sco_semset.py b/app/scodoc/sco_semset.py
index a91e8788c..10c06c9e3 100644
--- a/app/scodoc/sco_semset.py
+++ b/app/scodoc/sco_semset.py
@@ -89,7 +89,7 @@ class SemSet(dict):
         if semset_id:  # read existing set
             L = semset_list(cnx, args={"semset_id": semset_id})
             if not L:
-                raise ValueError("invalid semset_id %s" % semset_id)
+                raise ScoValueError(f"Ensemble inexistant ! (semset {semset_id})")
             self["title"] = L[0]["title"]
             self["annee_scolaire"] = L[0]["annee_scolaire"]
             self["sem_id"] = L[0]["sem_id"]