diff --git a/app/models/config.py b/app/models/config.py
index 8f6257bbc..613c3ccd0 100644
--- a/app/models/config.py
+++ b/app/models/config.py
@@ -464,7 +464,7 @@ class ScoDocSiteConfig(models.ScoDocModel):
     @classmethod
     def assi_get_rounded_time(cls, label: str, default: str) -> float:
         "Donne l'heure stockée dans la config globale sous label, en float arrondi au quart d'heure"
-        return _round_time_str_to_quarter(cls.get(label, default))
+        return _round_time_str_to_quarter(cls.get(label, default) or default)
 
 
 def _round_time_str_to_quarter(string: str) -> float: