diff --git a/src/calibre/ebooks/mobi/reader/headers.py b/src/calibre/ebooks/mobi/reader/headers.py
index f589df1945..ac7e076787 100644
--- a/src/calibre/ebooks/mobi/reader/headers.py
+++ b/src/calibre/ebooks/mobi/reader/headers.py
@@ -172,8 +172,8 @@ class BookHeader(object):
                 self.codec = 'cp1252' if not user_encoding else user_encoding
                 log.warn('Unknown codepage %d. Assuming %s' % (self.codepage,
                     self.codec))
-            # Some KF8 files have header length == 256. See
-            # https://bugs.launchpad.net/bugs/1067310
+            # Some KF8 files have header length == 256 (generated by kindlegen
+            # 2.7?). See https://bugs.launchpad.net/bugs/1067310
             max_header_length = 0x100
 
             if (ident == 'TEXTREAD' or self.length < 0xE4 or
diff --git a/src/calibre/ebooks/mobi/reader/mobi6.py b/src/calibre/ebooks/mobi/reader/mobi6.py
index 6dd789755d..a57e98b771 100644
--- a/src/calibre/ebooks/mobi/reader/mobi6.py
+++ b/src/calibre/ebooks/mobi/reader/mobi6.py
@@ -753,13 +753,13 @@ class MobiReader(object):
         processed_records = list(range(offset-1, self.book_header.records +
             offset))
 
-        self.mobi_html = ''
+        self.mobi_html = b''
 
         if self.book_header.compression_type == 'DH':
             huffs = [self.sections[i][0] for i in
-                range(self.book_header.huff_offset,
+                xrange(self.book_header.huff_offset,
                     self.book_header.huff_offset + self.book_header.huff_number)]
-            processed_records += list(range(self.book_header.huff_offset,
+            processed_records += list(xrange(self.book_header.huff_offset,
                 self.book_header.huff_offset + self.book_header.huff_number))
             huff = HuffReader(huffs)
             unpack = huff.unpack