diff --git a/src/calibre/ebooks/oeb/stylizer.py b/src/calibre/ebooks/oeb/stylizer.py
index 64ed2a45e8..7644bfc0c4 100644
--- a/src/calibre/ebooks/oeb/stylizer.py
+++ b/src/calibre/ebooks/oeb/stylizer.py
@@ -159,7 +159,7 @@ def __init__(self, tree, path, oeb, profile=PROFILES['PRS505']):
         for _, _, cssdict, text, _ in rules:
             try:
                 selector = CSSSelector(text)
-            except ExpressionError:
+            except (AssertionError, ExpressionError, etree.XPathSyntaxError):
                 continue
             for elem in selector(tree):
                 self.style(elem)._update_cssdict(cssdict)
diff --git a/src/calibre/ebooks/oeb/transforms/manglecase.py b/src/calibre/ebooks/oeb/transforms/manglecase.py
index 3a3d91364f..15dd8b9e14 100644
--- a/src/calibre/ebooks/oeb/transforms/manglecase.py
+++ b/src/calibre/ebooks/oeb/transforms/manglecase.py
@@ -6,13 +6,6 @@
 __license__   = 'GPL v3'
 __copyright__ = '2008, Marshall T. Vandegrift <llasram@gmail.com>'
 
-import sys
-import os
-import re
-import operator
-import math
-from itertools import chain
-from collections import defaultdict
 from lxml import etree
 from calibre.ebooks.oeb.base import XHTML, XHTML_NS
 from calibre.ebooks.oeb.base import CSS_MIME