diff --git a/src/agenda_culturel/models.py b/src/agenda_culturel/models.py
index 9f41c2d..e571def 100644
--- a/src/agenda_culturel/models.py
+++ b/src/agenda_culturel/models.py
@@ -1189,7 +1189,7 @@ class Event(models.Model):
         return self.imported_date is None or self.modified()
 
     def get_reference_urls(self):
-        res = [] if self.reference_urls is None else self.reference_urls
+        res = [] if self.reference_urls is None else copy.copy(self.reference_urls)
 
         if self.other_versions:
             for o in self.other_versions.get_duplicated():