diff --git a/setup/qt5-migrate.py b/setup/qt5-migrate.py
index c5bb637113..7efd3530ab 100644
--- a/setup/qt5-migrate.py
+++ b/setup/qt5-migrate.py
@@ -48,7 +48,7 @@ def all_py_files():
 
 def detect_qvariant():
     count = 0
-    pat = re.compile(b'|'.join(br'QVariant NONE toDateTime toDate toInt toBool toString\(\) toPyObject canConvert toBitArray toByteArray toHash toFloat toMap toLine toPoint toReal toRect toTime toUInt toUrl'.split()))  # noqa
+    pat = re.compile(b'|'.join(br'QVariant NONE toDateTime toDate toInt toBool toString\(\) toPyObject canConvert toBitArray toByteArray toHash toFloat toMap toLine toPoint toReal toRect toTime\(\) toUInt toUrl'.split()))  # noqa
     exclusions = {
         'src/calibre/gui2/viewer/gestures.py': {'toPoint'},
         'src/calibre/utils/serve_coffee.py': {'toString()'},
diff --git a/src/calibre/gui2/toc/location.py b/src/calibre/gui2/toc/location.py
index 245a3ca5ee..3f3a0c4ff9 100644
--- a/src/calibre/gui2/toc/location.py
+++ b/src/calibre/gui2/toc/location.py
@@ -88,8 +88,9 @@ class WebView(QWebView):  # {{{
 
     @property
     def scroll_frac(self):
-        val, ok = self.page().evaljs('window.pageYOffset/document.body.scrollHeight').toFloat()
-        if not ok:
+        try:
+            val = float(self.page().evaljs('window.pageYOffset/document.body.scrollHeight'))
+        except (TypeError, ValueError):
             val = 0
         return val
 # }}}
@@ -190,9 +191,9 @@ class ItemEdit(QWidget):
                     _('No match found for: %s')%text, show=True)
 
             delta = 1 if forwards else -1
-            current = unicode(d.currentItem().data(Qt.DisplayRole).toString())
+            current = unicode(d.currentItem().data(Qt.DisplayRole) or '')
             next_index = (d.currentRow() + delta)%d.count()
-            next = unicode(d.item(next_index).data(Qt.DisplayRole).toString())
+            next = unicode(d.item(next_index).data(Qt.DisplayRole) or '')
             msg = '<p>'+_('No matches for %(text)s found in the current file [%(current)s].'
                           ' Do you want to search in the %(which)s file [%(next)s]?')
             msg = msg%dict(text=text, current=current, next=next,
@@ -215,7 +216,7 @@ class ItemEdit(QWidget):
         self.dest_list.addItems(spine_names)
 
     def current_changed(self, item):
-        name = self.current_name = unicode(item.data(Qt.DisplayRole).toString())
+        name = self.current_name = unicode(item.data(Qt.DisplayRole) or '')
         path = self.container.name_to_abspath(name)
         # Ensure encoding map is populated
         root = self.container.parsed(name)
@@ -248,13 +249,13 @@ class ItemEdit(QWidget):
         dest_index, frag = 0, None
         if item is not None:
             if where is None:
-                self.name.setText(item.data(0, Qt.DisplayRole).toString())
+                self.name.setText(item.data(0, Qt.DisplayRole) or '')
                 self.name.setCursorPosition(0)
-            toc = item.data(0, Qt.UserRole).toPyObject()
+            toc = item.data(0, Qt.UserRole)
             if toc.dest:
                 for i in xrange(self.dest_list.count()):
                     litem = self.dest_list.item(i)
-                    if unicode(litem.data(Qt.DisplayRole).toString()) == toc.dest:
+                    if unicode(litem.data(Qt.DisplayRole) or '') == toc.dest:
                         dest_index = i
                         frag = toc.frag
                         break
diff --git a/src/calibre/gui2/toc/main.py b/src/calibre/gui2/toc/main.py
index a3ba6852e2..c326be2b95 100644
--- a/src/calibre/gui2/toc/main.py
+++ b/src/calibre/gui2/toc/main.py
@@ -11,7 +11,7 @@ import sys, os, textwrap
 from threading import Thread
 from functools import partial
 
-from PyQt5.Qt import (QPushButton, QFrame, QVariant, QMenu, QInputDialog,
+from PyQt5.Qt import (QPushButton, QFrame, QMenu, QInputDialog,
     QDialog, QVBoxLayout, QDialogButtonBox, QSize, QStackedWidget, QWidget,
     QLabel, Qt, pyqtSignal, QIcon, QTreeWidget, QGridLayout, QTreeWidgetItem,
     QToolButton, QItemSelectionModel, QCursor, QKeySequence)
@@ -330,12 +330,12 @@ class ItemView(QFrame):  # {{{
 
     def populate_item_pane(self):
         item = self.current_item
-        name = unicode(item.data(0, Qt.DisplayRole).toString())
+        name = unicode(item.data(0, Qt.DisplayRole) or '')
         self.item_pane.heading.setText('<h2>%s</h2>'%name)
         self.icon_label.setPixmap(item.data(0, Qt.DecorationRole
-                                            ).toPyObject().pixmap(32, 32))
+                                            ).pixmap(32, 32))
         tt = _('This entry points to an existing destination')
-        toc = item.data(0, Qt.UserRole).toPyObject()
+        toc = item.data(0, Qt.UserRole)
         if toc.dest_exists is False:
             tt = _('The location this entry points to does not exist')
         elif toc.dest_exists is None:
@@ -487,7 +487,7 @@ class TreeWidget(QTreeWidget):  # {{{
     def title_case(self):
         from calibre.utils.titlecase import titlecase
         for item in self.selectedItems():
-            t = unicode(item.data(0, Qt.DisplayRole).toString())
+            t = unicode(item.data(0, Qt.DisplayRole) or '')
             item.setData(0, Qt.DisplayRole, titlecase(t))
 
     def bulk_rename(self):
@@ -526,7 +526,7 @@ class TreeWidget(QTreeWidget):  # {{{
 
         if item is not None:
             m = QMenu()
-            ci = unicode(item.data(0, Qt.DisplayRole).toString())
+            ci = unicode(item.data(0, Qt.DisplayRole) or '')
             p = item.parent() or self.invisibleRootItem()
             idx = p.indexOfChild(item)
             if idx > 0:
@@ -622,7 +622,7 @@ class TOCView(QWidget):  # {{{
         return super(TOCView, self).event(e)
 
     def item_title(self, item):
-        return unicode(item.data(0, Qt.DisplayRole).toString())
+        return unicode(item.data(0, Qt.DisplayRole) or '')
 
     def del_items(self):
         self.tocw.del_items()
@@ -672,7 +672,7 @@ class TOCView(QWidget):  # {{{
         self.tocw.move_down()
 
     def update_status_tip(self, item):
-        c = item.data(0, Qt.UserRole).toPyObject()
+        c = item.data(0, Qt.UserRole)
         if c is not None:
             frag = c.frag or ''
             if frag:
@@ -683,8 +683,8 @@ class TOCView(QWidget):  # {{{
     def data_changed(self, top_left, bottom_right):
         for r in xrange(top_left.row(), bottom_right.row()+1):
             idx = self.tocw.model().index(r, 0, top_left.parent())
-            new_title = unicode(idx.data(Qt.DisplayRole).toString()).strip()
-            toc = idx.data(Qt.UserRole).toPyObject()
+            new_title = unicode(idx.data(Qt.DisplayRole) or '').strip()
+            toc = idx.data(Qt.UserRole)
             if toc is not None:
                 toc.title = new_title or _('(Untitled)')
             item = self.tocw.itemFromIndex(idx)
@@ -711,7 +711,7 @@ class TOCView(QWidget):  # {{{
                 'The location this entry point to does not exist:\n%s')
                 %child.dest_error)
         else:
-            c.setData(0, Qt.ToolTipRole, QVariant())
+            c.setData(0, Qt.ToolTipRole, None)
 
         self.update_status_tip(c)
 
@@ -774,8 +774,8 @@ class TOCView(QWidget):  # {{{
         def process_node(parent, toc_parent):
             for i in xrange(parent.childCount()):
                 item = parent.child(i)
-                title = unicode(item.data(0, Qt.DisplayRole).toString()).strip()
-                toc = item.data(0, Qt.UserRole).toPyObject()
+                title = unicode(item.data(0, Qt.DisplayRole) or '').strip()
+                toc = item.data(0, Qt.UserRole)
                 dest, frag = toc.dest, toc.frag
                 toc = toc_parent.add(title, dest, frag)
                 process_node(item, toc)
diff --git a/src/calibre/web/fetch/javascript.py b/src/calibre/web/fetch/javascript.py
index d7dfcf0a6a..71de02de83 100644
--- a/src/calibre/web/fetch/javascript.py
+++ b/src/calibre/web/fetch/javascript.py
@@ -101,14 +101,14 @@ def download_resources(browser, resource_cache, output_dir):
     for img in browser.css_select('img[src]', all=True):
         # Using javascript ensures that absolute URLs are returned, direct
         # attribute access does not do that
-        src = unicode(img.evaluateJavaScript('this.src').toString()).strip()
+        src = unicode(img.evaluateJavaScript('this.src') or '').strip()
         if src:
             resources[src].append(img)
     for link in browser.css_select('link[href]', all=True):
         lt = unicode(link.attribute('type')).strip() or 'text/css'
         rel = unicode(link.attribute('rel')).strip() or 'stylesheet'
         if lt == 'text/css' and rel == 'stylesheet':
-            href = unicode(link.evaluateJavaScript('this.href').toString()).strip()
+            href = unicode(link.evaluateJavaScript('this.href') or '').strip()
             if href:
                 resources[href].append(link)
             else:
@@ -165,7 +165,7 @@ def links_from_selectors(selectors, recursions, browser, url, recursion_level):
     if recursions > recursion_level:
         for selector in selectors:
             for a in browser.css_select(selector, all=True):
-                href = unicode(a.evaluateJavaScript('this.href').toString()).strip()
+                href = unicode(a.evaluateJavaScript('this.href') or '').strip()
                 if href:
                     ans.append(href)
     return ans
diff --git a/src/calibre/web/jsbrowser/browser.py b/src/calibre/web/jsbrowser/browser.py
index e6e1b73cbc..c58580cc56 100644
--- a/src/calibre/web/jsbrowser/browser.py
+++ b/src/calibre/web/jsbrowser/browser.py
@@ -125,7 +125,7 @@ class WebPage(QWebPage):  # {{{
 
     @property
     def ready_state(self):
-        return unicode(self.mainFrame().evaluateJavaScript('document.readyState').toString())
+        return unicode(self.mainFrame().evaluateJavaScript('document.readyState') or '')
 
     @pyqtSlot(QPixmap)
     def transfer_image(self, img):
@@ -210,7 +210,7 @@ class NetworkAccessManager(QNetworkAccessManager):  # {{{
         reply.ignoreSslErrors()
 
     def createRequest(self, operation, request, data):
-        url = unicode(request.url().toString())
+        url = unicode(request.url().toString(QUrl.None))
         operation_name = self.OPERATION_NAMES[operation]
         debug = []
         debug.append(('Request: %s %s' % (operation_name, url)))
@@ -245,7 +245,7 @@ class NetworkAccessManager(QNetworkAccessManager):  # {{{
             self.report_reply(reply)
 
     def report_reply(self, reply):
-        reply_url = unicode(reply.url().toString())
+        reply_url = unicode(reply.url().toString(QUrl.None))
         self.reply_count += 1
         err = reply.error()