diff --git a/resources/compiled_coffeescript.zip b/resources/compiled_coffeescript.zip
index 275739a8af..4b5ab2b972 100644
Binary files a/resources/compiled_coffeescript.zip and b/resources/compiled_coffeescript.zip differ
diff --git a/src/calibre/ebooks/oeb/polish/preview.coffee b/src/calibre/ebooks/oeb/polish/preview.coffee
index 514ea329ce..40fa2d4f97 100644
--- a/src/calibre/ebooks/oeb/polish/preview.coffee
+++ b/src/calibre/ebooks/oeb/polish/preview.coffee
@@ -95,7 +95,7 @@ class PreviewIntegration
             loc.push(num)
             parent = parent.parentNode
         loc.reverse()
-        window.py_bridge.request_split(loc)
+        window.py_bridge.request_split(JSON.stringify(loc))
 
     onload: () =>
         window.document.body.addEventListener('click', this.onclick, true)
diff --git a/src/calibre/gui2/tweak_book/preview.py b/src/calibre/gui2/tweak_book/preview.py
index c25dfc303a..a2b8ecf00e 100644
--- a/src/calibre/gui2/tweak_book/preview.py
+++ b/src/calibre/gui2/tweak_book/preview.py
@@ -6,7 +6,7 @@ from __future__ import (unicode_literals, division, absolute_import,
 __license__ = 'GPL v3'
 __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 
-import time, textwrap
+import time, textwrap, json
 from bisect import bisect_right
 from base64 import b64encode
 from future_builtins import map
@@ -319,9 +319,10 @@ class WebPage(QWebPage):
         except (TypeError, ValueError, OverflowError, AttributeError):
             pass
 
-    @pyqtSlot('QList<int>')
+    @pyqtSlot(str)
     def request_split(self, loc):
         actions['split-in-preview'].setChecked(False)
+        loc = json.loads(unicode(loc))
         if not loc:
             return error_dialog(self.view(), _('Invalid location'),
                                 _('Cannot split on the body tag'), show=True)