diff --git a/apps/registration/auth.py b/apps/registration/auth.py
index 779aee3..4014de5 100644
--- a/apps/registration/auth.py
+++ b/apps/registration/auth.py
@@ -1,5 +1,4 @@
 from cas_server.auth import DjangoAuthUser
-from django.utils.text import slugify
 
 
 class CustomAuthUser(DjangoAuthUser):
@@ -10,5 +9,5 @@ class CustomAuthUser(DjangoAuthUser):
     def attributs(self):
         d = super().attributs()
         if self.user:
-            d["matrix_username"] = slugify(str(self.user.registration))
+            d["matrix_username"] = f"corres2math_{self.user.pk}"
         return d