diff --git a/src/calibre/gui2/tweak_book/editor/syntax/base.py b/src/calibre/gui2/tweak_book/editor/syntax/base.py
index b0043815ae..752d4e8ab4 100644
--- a/src/calibre/gui2/tweak_book/editor/syntax/base.py
+++ b/src/calibre/gui2/tweak_book/editor/syntax/base.py
@@ -228,7 +228,7 @@ class SyntaxHighlighter(object):
     def apply_format_changes(self, block, formats):
         layout = block.layout()
         preedit_start = layout.preeditAreaPosition()
-        preedit_length = layout.preeditAreaText().length()
+        preedit_length = len(layout.preeditAreaText())
         if preedit_length != 0 and preedit_start != 0:
             for r in formats:
                 # Adjust range by pre-edit text, if any
diff --git a/src/calibre/gui2/tweak_book/editor/syntax/css.py b/src/calibre/gui2/tweak_book/editor/syntax/css.py
index 0af0ad300d..4f6d5c7f11 100644
--- a/src/calibre/gui2/tweak_book/editor/syntax/css.py
+++ b/src/calibre/gui2/tweak_book/editor/syntax/css.py
@@ -8,7 +8,7 @@ __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 
 import re
 
-from PyQt4.Qt import QTextBlockUserData
+from PyQt5.Qt import QTextBlockUserData
 
 from calibre.gui2.tweak_book import verify_link
 from calibre.gui2.tweak_book.editor import syntax_text_char_format, LINK_PROPERTY, CSS_PROPERTY