diff --git a/Lib/imaplib.py b/Lib/imaplib.py
index 4b8e898..1022e77 100644
--- a/Lib/imaplib.py
+++ b/Lib/imaplib.py
@@ -1308,8 +1308,8 @@
 
 
 
-Mon2num = {'Jan': 1, 'Feb': 2, 'Mar': 3, 'Apr': 4, 'May': 5, 'Jun': 6,
-        'Jul': 7, 'Aug': 8, 'Sep': 9, 'Oct': 10, 'Nov': 11, 'Dec': 12}
+Mon2num = {b'Jan': 1, b'Feb': 2, b'Mar': 3, b'Apr': 4, b'May': 5, b'Jun': 6,
+           b'Jul': 7, b'Aug': 8, b'Sep': 9, b'Oct': 10, b'Nov': 11, b'Dec': 12}
 
 def Internaldate2tuple(resp):
     """Parse an IMAP4 INTERNALDATE string.
@@ -1336,7 +1336,7 @@
     # INTERNALDATE timezone must be subtracted to get UT
 
     zone = (zoneh*60 + zonem)*60
-    if zonen == '-':
+    if zonen == b'-':
         zone = -zone
 
     tt = (year, mon, day, hour, min, sec, -1, -1, -1)