1 files changed, 2 insertions, 2 deletions

diff --git a/src/mailman/rest/users.py b/src/mailman/rest/users.py
index 7e6e70c5a..c8e3475e7 100644
--- a/src/mailman/rest/users.py
+++ b/src/mailman/rest/users.py
@@ -122,8 +122,8 @@ class AllUsers(_UserBase):
         try:
             user = getUtility(IUserManager).create_user(**arguments)
         except ExistingAddressError as error:
-            bad_request(
-                response, b'Address already exists: {0}'.format(error.address))
+            reason = 'Address already exists: {}'.format(error.address)
+            bad_request(response, reason.encode('utf-8'))
             return
         if password is None:
             # This will have to be reset since it cannot be retrieved.