diff --git a/imap_filter/imap_filter.py b/imap_filter/imap_filter.py
index bdc031d..ce9f114 100644
--- a/imap_filter/imap_filter.py
+++ b/imap_filter/imap_filter.py
@@ -90,7 +90,7 @@ class ImapFilter:
                     self._log.warning(
                         "Missing required field '%s' in mailbox '%s', skipping.",
                         field,
-                        mailbox
+                        mailbox.keys()
                     )
                     break
             self.connect_imap(