diff --git a/offlineimap/folder/IMAP.py b/offlineimap/folder/IMAP.py
index 253ac97..9ed7fec 100644
--- a/offlineimap/folder/IMAP.py
+++ b/offlineimap/folder/IMAP.py
@@ -489,7 +489,7 @@ class IMAPFolder(BaseFolder):
 
         # tm_isdst coming from email.parsedate is not usable, we still use it
         # here, mhh.
-        if datetuple.tm_isdst == '1':
+        if datetuple.tm_isdst == 1:
             zone = -time.altzone
         else:
             zone = -time.timezone