diff --git a/src/yunohost/app.py b/src/yunohost/app.py
index 0caa9d5e1..8cf83e594 100644
--- a/src/yunohost/app.py
+++ b/src/yunohost/app.py
@@ -2567,7 +2567,7 @@ def _parse_args_in_yunohost_format(user_answers, argument_questions):
 
                     root_mail = "root@%s" % _get_maindomain()
                     for user in users.keys():
-                        if root_mail in user_info(user)["mail-aliases"]:
+                        if root_mail in user_info(user).get("mail-aliases", []):
                             question_default = user
                             break