diff --git a/src/calibre/customize/builtins.py b/src/calibre/customize/builtins.py
index bba5b1e83b..9321e7e9c8 100644
--- a/src/calibre/customize/builtins.py
+++ b/src/calibre/customize/builtins.py
@@ -1,4 +1,5 @@
 # -*- coding: utf-8 -*-
+from __future__ import absolute_import, division, print_function, unicode_literals
 
 __license__   = 'GPL v3'
 __copyright__ = '2008, Kovid Goyal <kovid at kovidgoyal.net>'
@@ -10,7 +11,6 @@ from calibre.customize import (FileTypePlugin, MetadataReaderPlugin,
 from calibre.constants import numeric_version
 from calibre.ebooks.metadata.archive import ArchiveExtract, get_comic_metadata
 from calibre.ebooks.html.to_zip import HTML2ZIP
-from polyglot.builtins import unicode_type
 
 plugins = []
 
@@ -65,23 +65,23 @@ class TXT2TXTZ(FileTypePlugin):
         images = []
 
         # Textile
-        for m in re.finditer(unicode_type(r'(?mu)(?:[\[{])?\!(?:\. )?(?P<path>[^\s(!]+)\s?(?:\(([^\)]+)\))?\!(?::(\S+))?(?:[\]}]|(?=\s|$))'), txt):
+        for m in re.finditer(r'(?mu)(?:[\[{])?\!(?:\. )?(?P<path>[^\s(!]+)\s?(?:\(([^\)]+)\))?\!(?::(\S+))?(?:[\]}]|(?=\s|$))', txt):
             path = m.group('path')
             if path and not os.path.isabs(path) and guess_type(path)[0] in OEB_IMAGES and os.path.exists(os.path.join(base_dir, path)):
                 images.append(path)
 
         # Markdown inline
-        for m in re.finditer(unicode_type(r'(?mu)\!\[([^\]\[]*(\[[^\]\[]*(\[[^\]\[]*(\[[^\]\[]*(\[[^\]\[]*(\[[^\]\[]*(\[[^\]\[]*\])*[^\]\[]*\])*[^\]\[]*\])*[^\]\[]*\])*[^\]\[]*\])*[^\]\[]*\])*[^\]\[]*)\]\s*\((?P<path>[^\)]*)\)'), txt):  # noqa
+        for m in re.finditer(r'(?mu)\!\[([^\]\[]*(\[[^\]\[]*(\[[^\]\[]*(\[[^\]\[]*(\[[^\]\[]*(\[[^\]\[]*(\[[^\]\[]*\])*[^\]\[]*\])*[^\]\[]*\])*[^\]\[]*\])*[^\]\[]*\])*[^\]\[]*\])*[^\]\[]*)\]\s*\((?P<path>[^\)]*)\)', txt):  # noqa
             path = m.group('path')
             if path and not os.path.isabs(path) and guess_type(path)[0] in OEB_IMAGES and os.path.exists(os.path.join(base_dir, path)):
                 images.append(path)
 
         # Markdown reference
         refs = {}
-        for m in re.finditer(unicode_type(r'(?mu)^(\ ?\ ?\ ?)\[(?P<id>[^\]]*)\]:\s*(?P<path>[^\s]*)$'), txt):
+        for m in re.finditer(r'(?mu)^(\ ?\ ?\ ?)\[(?P<id>[^\]]*)\]:\s*(?P<path>[^\s]*)$', txt):
             if m.group('id') and m.group('path'):
                 refs[m.group('id')] = m.group('path')
-        for m in re.finditer(unicode_type(r'(?mu)\!\[([^\]\[]*(\[[^\]\[]*(\[[^\]\[]*(\[[^\]\[]*(\[[^\]\[]*(\[[^\]\[]*(\[[^\]\[]*\])*[^\]\[]*\])*[^\]\[]*\])*[^\]\[]*\])*[^\]\[]*\])*[^\]\[]*\])*[^\]\[]*)\]\s*\[(?P<id>[^\]]*)\]'), txt):  # noqa
+        for m in re.finditer(r'(?mu)\!\[([^\]\[]*(\[[^\]\[]*(\[[^\]\[]*(\[[^\]\[]*(\[[^\]\[]*(\[[^\]\[]*(\[[^\]\[]*\])*[^\]\[]*\])*[^\]\[]*\])*[^\]\[]*\])*[^\]\[]*\])*[^\]\[]*\])*[^\]\[]*)\]\s*\[(?P<id>[^\]]*)\]', txt):  # noqa
             path = refs.get(m.group('id'), None)
             if path and not os.path.isabs(path) and guess_type(path)[0] in OEB_IMAGES and os.path.exists(os.path.join(base_dir, path)):
                 images.append(path)
@@ -93,7 +93,7 @@ class TXT2TXTZ(FileTypePlugin):
         from calibre.ebooks.metadata.opf2 import metadata_to_opf
 
         with open(path_to_ebook, 'rb') as ebf:
-            txt = ebf.read()
+            txt = ebf.read().decode('utf-8', 'replace')
         base_dir = os.path.dirname(path_to_ebook)
         images = self._get_image_references(txt, base_dir)