diff --git a/app/scodoc/sco_edit_module.py b/app/scodoc/sco_edit_module.py
index b94a60178..2e8c9ca71 100644
--- a/app/scodoc/sco_edit_module.py
+++ b/app/scodoc/sco_edit_module.py
@@ -236,6 +236,7 @@ def do_module_edit(vals: dict) -> None:
     mod = module_list({"module_id": vals["module_id"]})[0]
     if module_is_locked(mod["module_id"]):
         # formation verrouillée: empeche de modifier certains champs:
+        vals = vals.copy()
         protected_fields = ("coefficient", "ue_id", "matiere_id", "semestre_id")
         for f in protected_fields:
             if f in vals: