diff --git a/src/calibre/gui2/tag_browser/model.py b/src/calibre/gui2/tag_browser/model.py
index 4415b372ea..75ea12470e 100644
--- a/src/calibre/gui2/tag_browser/model.py
+++ b/src/calibre/gui2/tag_browser/model.py
@@ -8,7 +8,7 @@ __license__   = 'GPL v3'
 __copyright__ = '2011, Kovid Goyal <kovid@kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
-import traceback, cPickle, copy, os
+import traceback, copy, os
 from collections import OrderedDict
 
 from PyQt5.Qt import (QAbstractItemModel, QIcon, QFont, Qt,
@@ -24,6 +24,8 @@ from calibre.library.field_metadata import category_icon_map
 from calibre.gui2.dialogs.confirm_delete import confirm
 from calibre.utils.formatter import EvalFormatter
 from polyglot.builtins import range
+from calibre.utils.serialize import json_dumps, json_loads
+
 
 TAG_SEARCH_STATES = {'clear': 0, 'mark_plus': 1, 'mark_plusplus': 2,
                      'mark_minus': 3, 'mark_minusminus': 4}
@@ -740,7 +742,7 @@ class TagsModel(QAbstractItemModel):  # {{{
                 data.append(d)
             else:
                 data.append(None)
-        raw = bytearray(cPickle.dumps(data, -1))
+        raw = bytearray(json_dumps(data))
         ans = QMimeData()
         ans.setData('application/calibre+from_tag_browser', raw)
         return ans
@@ -764,8 +766,8 @@ class TagsModel(QAbstractItemModel):  # {{{
             return False
         if not md.hasFormat('application/calibre+from_tag_browser'):
             return False
-        data = str(md.data('application/calibre+from_tag_browser'))
-        src = cPickle.loads(data)
+        data = bytes(md.data('application/calibre+from_tag_browser'))
+        src = json_loads(data)
         for s in src:
             if s[0] != TagTreeItem.TAG:
                 return False
diff --git a/src/calibre/gui2/tag_browser/view.py b/src/calibre/gui2/tag_browser/view.py
index 49a064257e..e19e7c9f15 100644
--- a/src/calibre/gui2/tag_browser/view.py
+++ b/src/calibre/gui2/tag_browser/view.py
@@ -7,7 +7,7 @@ __license__   = 'GPL v3'
 __copyright__ = '2011, Kovid Goyal <kovid@kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
-import cPickle, os, re
+import os, re
 from functools import partial
 from itertools import izip
 
@@ -24,6 +24,7 @@ from calibre.gui2.tag_browser.model import (TagTreeItem, TAG_SEARCH_STATES,
         TagsModel, DRAG_IMAGE_ROLE, COUNT_ROLE)
 from calibre.gui2 import config, gprefs, choose_files, pixmap_to_data, rating_font, empty_index
 from calibre.utils.icu import sort_key
+from calibre.utils.serialize import json_loads
 from polyglot.builtins import unicode_type, range
 
 
@@ -751,8 +752,8 @@ class TagsView(QTreeView):  # {{{
             if fm_dest['kind'] == 'user':
                 if src_is_tb:
                     if event.dropAction() == Qt.MoveAction:
-                        data = str(event.mimeData().data('application/calibre+from_tag_browser'))
-                        src = cPickle.loads(data)
+                        data = bytes(event.mimeData().data('application/calibre+from_tag_browser'))
+                        src = json_loads(data)
                         for s in src:
                             if s[0] == TagTreeItem.TAG and \
                                     (not s[1].startswith('@') or s[2]):