diff --git a/app/models/formations.py b/app/models/formations.py
index 1dfd8728..e926471c 100644
--- a/app/models/formations.py
+++ b/app/models/formations.py
@@ -4,6 +4,7 @@
 from app import db
 from app.comp import df_cache
 from app.models import SHORT_STR_LEN
+from app.models.modules import Module
 from app.scodoc import notesdb as ndb
 from app.scodoc import sco_cache
 from app.scodoc import sco_codes_parcours
@@ -114,6 +115,7 @@ class Formation(db.Model):
             return
         change = False
         for mod in self.modules:
+            # --- Indices de semestres:
             if (
                 mod.ue.semestre_idx is not None
                 and mod.ue.semestre_idx > 0
@@ -122,10 +124,15 @@ class Formation(db.Model):
                 mod.semestre_id = mod.ue.semestre_idx
                 db.session.add(mod)
                 change = True
+            # --- Types de modules
             if mod.module_type is None:
                 mod.module_type = scu.ModuleType.STANDARD
                 db.session.add(mod)
                 change = True
+        # --- Numéros de modules
+        if Module.query.filter_by(formation_id=220, numero=None).count() > 0:
+            scu.objects_renumber(db, self.modules.all())
+
         db.session.commit()
         if change:
             self.invalidate_module_coefs()
diff --git a/app/scodoc/sco_edit_formation.py b/app/scodoc/sco_edit_formation.py
index a126fceb..cb8c816a 100644
--- a/app/scodoc/sco_edit_formation.py
+++ b/app/scodoc/sco_edit_formation.py
@@ -306,7 +306,6 @@ def do_formation_edit(args):
     sco_formations._formationEditor.edit(cnx, args)
     formation: Formation = Formation.query.get(args["formation_id"])
     formation.invalidate_cached_sems()
-    formation.sanitize_old_formation()
 
 
 def module_move(module_id, after=0, redirect=True):
diff --git a/app/scodoc/sco_edit_ue.py b/app/scodoc/sco_edit_ue.py
index 14f8a2c9..abda43bd 100644
--- a/app/scodoc/sco_edit_ue.py
+++ b/app/scodoc/sco_edit_ue.py
@@ -509,7 +509,6 @@ def ue_table(formation_id=None, semestre_idx=1, msg=""):  # was ue_list
     formation: Formation = Formation.query.get(formation_id)
     if not formation:
         raise ScoValueError("invalid formation_id")
-    formation.sanitize_old_formation()
     parcours = formation.get_parcours()
     is_apc = parcours.APC_SAE
     locked = formation.has_locked_sems()
@@ -1205,7 +1204,6 @@ def do_ue_edit(args, bypass_lock=False, dont_invalidate_cache=False):
     if not dont_invalidate_cache:
         # Invalide les semestres utilisant cette formation:
         formation.invalidate_cached_sems()
-    formation.sanitize_old_formation()
 
 
 # essai edition en ligne:
diff --git a/sco_version.py b/sco_version.py
index 27206370..aabbc6ca 100644
--- a/sco_version.py
+++ b/sco_version.py
@@ -1,7 +1,7 @@
 # -*- mode: python -*-
 # -*- coding: utf-8 -*-
 
-SCOVERSION = "9.1.19"
+SCOVERSION = "9.1.20"
 
 SCONAME = "ScoDoc"
 
diff --git a/scodoc.py b/scodoc.py
index 94c8a7f0..03f656a7 100755
--- a/scodoc.py
+++ b/scodoc.py
@@ -438,14 +438,21 @@ def photos_import_files(formsemestre_id: int, xlsfile: str, zipfile: str):
 
 
 @app.cli.command()
+@click.option("--sanitize/--no-sanitize", default=False)
 @with_appcontext
-def clear_cache():  # clear-cache
+def clear_cache(sanitize):  # clear-cache
     """Clear ScoDoc cache
     This cache (currently Redis) is persistent between invocation
-    and it may be necessary to clear it during development or tests.
+    and it may be necessary to clear it during upgrades,
+    development or tests.
     """
+    click.echo("Flushing Redis cache...")
     clear_scodoc_cache()
-    click.echo("Redis caches flushed.")
+    if sanitize:
+        # sanitizes all formations:
+        click.echo("Checking formations...")
+        for formation in Formation.query:
+            formation.sanitize_old_formation()
 
 
 def recursive_help(cmd, parent=None):
diff --git a/tools/debian/postinst b/tools/debian/postinst
index 84001fc9..33a705c2 100755
--- a/tools/debian/postinst
+++ b/tools/debian/postinst
@@ -107,7 +107,7 @@ then
     # utilise les scripts dans migrations/version/
     # pour mettre à jour notre base (en tant qu'utilisateur scodoc)
     export FLASK_ENV="production"
-    su -c "(cd $SCODOC_DIR && source venv/bin/activate && flask db upgrade && flask clear-cache)" "$SCODOC_USER"
+    su -c "(cd $SCODOC_DIR && source venv/bin/activate && flask db upgrade && flask clear-cache --sanitize)" "$SCODOC_USER"
 fi
 
 # ------------ LOGROTATE