diff --git a/py3/chapter15/open_imap.py b/py3/chapter15/open_imap.py
index 17a6d33..fea47ee 100644
--- a/py3/chapter15/open_imap.py
+++ b/py3/chapter15/open_imap.py
@@ -22,7 +22,7 @@ def main():
         print('Listing mailboxes:')
         data = c.list_folders()
         for flags, delimiter, folder_name in data:
-            print('  %-30s%s %s' % (' '.join(flags), delimiter, folder_name))
+            print('  %-30s%s %s' % (b' '.join(flags), delimiter, folder_name))
     finally:
         c.logout()