diff --git a/mondumas/views/default.py b/mondumas/views/default.py
index 3ee129e..6700ee4 100644
--- a/mondumas/views/default.py
+++ b/mondumas/views/default.py
@@ -74,7 +74,7 @@ def to_percent(x):
     return ("%.2f " % x).replace('.', ',') + "%"
 
 def generate_auth_string(user, token):
-    return f"user={user}\x01auth=Bearer {token}\x01\x01"    
+    return "user=%s\x01auth=Bearer %s\x01\x01" % (user, token)
 
 def mailbox_connect(request, societe):
     # connecter au serveur IMAP de la societe