diff --git a/src/calibre/gui2/tweak_book/editor/__init__.py b/src/calibre/gui2/tweak_book/editor/__init__.py
index caf01372b9..76a59f6a67 100644
--- a/src/calibre/gui2/tweak_book/editor/__init__.py
+++ b/src/calibre/gui2/tweak_book/editor/__init__.py
@@ -6,6 +6,8 @@ from __future__ import (unicode_literals, division, absolute_import,
 __license__ = 'GPL v3'
 __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 
+from PyQt4.Qt import QTextCharFormat
+
 from calibre.ebooks.oeb.base import OEB_DOCS, OEB_STYLES
 from calibre.ebooks.oeb.polish.container import guess_type
 
@@ -25,3 +27,11 @@ def editor_from_syntax(syntax, parent=None):
     from calibre.gui2.tweak_book.editor.widget import Editor
     return Editor(syntax, parent=parent)
 
+SYNTAX_PROPERTY = QTextCharFormat.UserProperty
+
+class SyntaxTextCharFormat(QTextCharFormat):
+
+    def __init__(self, *args, **kwargs):
+        QTextCharFormat.__init__(self, *args, **kwargs)
+        self.setProperty(SYNTAX_PROPERTY, True)
+
diff --git a/src/calibre/gui2/tweak_book/editor/syntax/css.py b/src/calibre/gui2/tweak_book/editor/syntax/css.py
index 5de019d172..4addf3ca3c 100644
--- a/src/calibre/gui2/tweak_book/editor/syntax/css.py
+++ b/src/calibre/gui2/tweak_book/editor/syntax/css.py
@@ -8,10 +8,9 @@ __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 
 import re
 
+from calibre.gui2.tweak_book.editor import SyntaxTextCharFormat
 from calibre.gui2.tweak_book.editor.syntax.base import SyntaxHighlighter
 
-from PyQt4.Qt import QTextCharFormat
-
 space_pat = re.compile(r'[ \n\t\r\f]+')
 cdo_pat = re.compile(r'/\*')
 sheet_tokens = [(re.compile(k), v, n) for k, v, n in [
@@ -242,7 +241,7 @@ def create_formats(highlighter):
         'unknown-normal': _('Invalid text'),
         'unterminated-string': _('Unterminated string'),
     }.iteritems():
-        f = formats[name] = QTextCharFormat(formats['error'])
+        f = formats[name] = SyntaxTextCharFormat(formats['error'])
         f.setToolTip(msg)
     return formats
 
diff --git a/src/calibre/gui2/tweak_book/editor/syntax/html.py b/src/calibre/gui2/tweak_book/editor/syntax/html.py
index 94479e4a5b..fd7e238de7 100644
--- a/src/calibre/gui2/tweak_book/editor/syntax/html.py
+++ b/src/calibre/gui2/tweak_book/editor/syntax/html.py
@@ -9,8 +9,9 @@ __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 import re
 from functools import partial
 
-from PyQt4.Qt import (QTextCharFormat, QFont)
+from PyQt4.Qt import QFont
 
+from calibre.gui2.tweak_book.editor import SyntaxTextCharFormat
 from calibre.gui2.tweak_book.editor.syntax.base import SyntaxHighlighter, run_loop
 from calibre.gui2.tweak_book.editor.syntax.css import create_formats as create_css_formats, state_map as css_state_map, State as CSSState
 
@@ -109,7 +110,7 @@ def mark_nbsp(state, text, nbsp_format):
     ans = []
     fmt = None
     if state.bold or state.italic:
-        fmt = QTextCharFormat()
+        fmt = SyntaxTextCharFormat()
         if state.bold:
             fmt.setFontWeight(QFont.Bold)
         if state.italic:
@@ -313,9 +314,9 @@ def create_formats(highlighter):
         'bad-closing': _('A closing tag must contain only the tag name and nothing else'),
         'no-attr-value': _('Expecting an attribute value'),
     }.iteritems():
-        f = formats[name] = QTextCharFormat(formats['error'])
+        f = formats[name] = SyntaxTextCharFormat(formats['error'])
         f.setToolTip(msg)
-    f = formats['title'] = QTextCharFormat()
+    f = formats['title'] = SyntaxTextCharFormat()
     f.setFontWeight(QFont.Bold)
     return formats
 
diff --git a/src/calibre/gui2/tweak_book/editor/text.py b/src/calibre/gui2/tweak_book/editor/text.py
index afd3e8c6dc..cbd5f2115d 100644
--- a/src/calibre/gui2/tweak_book/editor/text.py
+++ b/src/calibre/gui2/tweak_book/editor/text.py
@@ -14,6 +14,7 @@ from PyQt4.Qt import (
     QTextEdit, QTextFormat, QWidget, QSize, QPainter, Qt, QRect)
 
 from calibre.gui2.tweak_book import tprefs
+from calibre.gui2.tweak_book.editor import SYNTAX_PROPERTY
 from calibre.gui2.tweak_book.editor.themes import THEMES, default_theme, theme_color
 from calibre.gui2.tweak_book.editor.syntax.base import SyntaxHighlighter
 from calibre.gui2.tweak_book.editor.syntax.html import HTMLHighlighter, XMLHighlighter
@@ -211,7 +212,7 @@ class TextEdit(QPlainTextEdit):
             return
         pos = cursor.positionInBlock()
         for r in cursor.block().layout().additionalFormats():
-            if r.start <= pos < r.start + r.length:
+            if r.start <= pos < r.start + r.length and r.format.property(SYNTAX_PROPERTY).toBool():
                 return r.format
 
     def show_tooltip(self, ev):
diff --git a/src/calibre/gui2/tweak_book/editor/themes.py b/src/calibre/gui2/tweak_book/editor/themes.py
index ed7cb3b596..ac94e9b134 100644
--- a/src/calibre/gui2/tweak_book/editor/themes.py
+++ b/src/calibre/gui2/tweak_book/editor/themes.py
@@ -8,7 +8,9 @@ __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 
 from collections import namedtuple
 
-from PyQt4.Qt import (QColor, QTextCharFormat, QBrush, QFont, QApplication, QPalette)
+from PyQt4.Qt import (QColor, QBrush, QFont, QApplication, QPalette)
+
+from calibre.gui2.tweak_book.editor import SyntaxTextCharFormat
 
 underline_styles = {'single', 'dash', 'dot', 'dash_dot', 'dash_dot_dot', 'wave', 'spell'}
 
@@ -198,10 +200,10 @@ def u(x):
     if 'Dot' in x:
         return x + 'Line'
     return x + 'Underline'
-underline_styles = {x:getattr(QTextCharFormat, u(x)) for x in underline_styles}
+underline_styles = {x:getattr(SyntaxTextCharFormat, u(x)) for x in underline_styles}
 
 def highlight_to_char_format(h):
-    ans = QTextCharFormat()
+    ans = SyntaxTextCharFormat()
     if h.bold:
         ans.setFontWeight(QFont.Bold)
     if h.italic: