diff --git a/offlineimap/folder/IMAP.py b/offlineimap/folder/IMAP.py
index efeafa7..3988681 100644
--- a/offlineimap/folder/IMAP.py
+++ b/offlineimap/folder/IMAP.py
@@ -219,7 +219,7 @@ class IMAPFolder(BaseFolder):
                                        OfflineImapError.ERROR.FOLDER)
             # Davmail returns list instead of list of one element string.
             # On first run the first element is empty.
-            if ' ' in res_data[0] or res_data[0] == '':
+            if b' ' in res_data[0] or res_data[0] == b'':
                 res_data = res_data[0].split()
             # Some servers are broken.
             if 0 in res_data: