diff --git a/src/calibre/gui2/tweak_book/preview.py b/src/calibre/gui2/tweak_book/preview.py
index 3796b18e68..53c0ba1794 100644
--- a/src/calibre/gui2/tweak_book/preview.py
+++ b/src/calibre/gui2/tweak_book/preview.py
@@ -7,7 +7,6 @@ from __future__ import absolute_import, division, print_function, unicode_litera
 # live css
 # check that clicking on both internal and external links works
 
-import json
 import textwrap
 import time
 from collections import defaultdict
@@ -35,7 +34,7 @@ from calibre.gui2.tweak_book import TOP, actions, current_container, editors, tp
 from calibre.gui2.webengine import create_script, insert_scripts, secure_webengine
 from calibre.gui2.widgets2 import HistoryLineEdit2
 from calibre.utils.ipc.simple_worker import offload_worker
-from polyglot.builtins import native_string_type, unicode_type
+from polyglot.builtins import unicode_type
 from polyglot.queue import Empty, Queue
 from polyglot.urllib import urlparse
 
@@ -293,10 +292,11 @@ class Bridge(QObject):
     def __init__(self, parent=None):
         QObject.__init__(self, parent)
 
-    @pyqtSlot(native_string_type, native_string_type, native_string_type)
+    @pyqtSlot('QString', 'QString', 'QJsonArray')
     def request_sync(self, tag_name, href, sourceline_address):
+        address = [sourceline_address[0].toInt(), [x.toString() for x in sourceline_address[1].toArray()]]
         try:
-            self.sync_requested.emit(unicode_type(tag_name), unicode_type(href), json.loads(unicode_type(sourceline_address)))
+            self.sync_requested.emit(tag_name, href, address)
         except (TypeError, ValueError, OverflowError, AttributeError):
             pass
 
diff --git a/src/pyj/editor.pyj b/src/pyj/editor.pyj
index 80d9b3eab3..b1d583cccc 100644
--- a/src/pyj/editor.pyj
+++ b/src/pyj/editor.pyj
@@ -142,7 +142,7 @@ INHERITED_PROPS = {  # {{{
 
 
 def get_sourceline_address(node):
-    sourceline = parseInt(node.getAttribute('data-lnum'))
+    sourceline = parseInt(node.dataset.lnum)
     tags = v'[]'
     for elem in document.querySelectorAll(f'[data-lnum="{sourceline}"]'):
         tags.push(elem.tagName.toLowerCase())
@@ -340,7 +340,7 @@ class PreviewIntegration:
                 tn = e.tagName.toLowerCase() if e.tagName else ''
                 href = e.getAttribute('href')
                 e = e.parentNode
-            self.bridge.request_sync(tn, href, JSON.stringify(address))
+            self.bridge.request_sync(tn, href, address)
         return False
 
     def go_to_anchor(self, anchor):