diff --git a/src/calibre/library/caches.py b/src/calibre/library/caches.py
index 943e414c1a..d9ff43a67c 100644
--- a/src/calibre/library/caches.py
+++ b/src/calibre/library/caches.py
@@ -6,7 +6,7 @@ __license__   = 'GPL v3'
 __copyright__ = '2010, Kovid Goyal <kovid@kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
-import re, itertools, time, traceback, copy
+import re, itertools, time, traceback
 from itertools import repeat, izip
 from datetime import timedelta
 from threading import Thread
@@ -790,7 +790,7 @@ class ResultCache(SearchQueryParser): # {{{
             # Simple list. Make it a dict of string 'true'
             self.marked_ids_dict = dict(izip(id_dict, repeat(u'true')))
         else:
-            self.marked_ids_dict = copy.copy(id_dict)
+            self.marked_ids_dict = id_dict.copy()
             # Ensure that all the items in the dict are text
             for id_,val in self.marked_ids_dict.iteritems():
                 self.marked_ids_dict[id_] = unicode(val)