diff --git a/src/calibre/gui2/tag_browser/model.py b/src/calibre/gui2/tag_browser/model.py
index 5589a1bcb4..e759783d7b 100644
--- a/src/calibre/gui2/tag_browser/model.py
+++ b/src/calibre/gui2/tag_browser/model.py
@@ -514,7 +514,7 @@ class TagsModel(QAbstractItemModel): # {{{
         # }}}
 
         for category in self.category_nodes:
-            process_one_node(category, state_map.get(category.py_name, {}))
+            process_one_node(category, state_map.get(category.category_key, {}))
 
     # Drag'n Drop {{{
     def mimeTypes(self):
@@ -851,7 +851,7 @@ class TagsModel(QAbstractItemModel): # {{{
 
     def index_for_category(self, name):
         for row, category in enumerate(self.category_nodes):
-            if category.py_name == name:
+            if category.category_key == name:
                 return self.index(row, 0, QModelIndex())
 
     def columnCount(self, parent):
diff --git a/src/calibre/gui2/tag_browser/view.py b/src/calibre/gui2/tag_browser/view.py
index 1fad4eb9a3..c833f7fa43 100644
--- a/src/calibre/gui2/tag_browser/view.py
+++ b/src/calibre/gui2/tag_browser/view.py
@@ -129,10 +129,10 @@ class TagsView(QTreeView): # {{{
         expanded_categories = []
         for row, category in enumerate(self._model.category_nodes):
             if self.isExpanded(self._model.index(row, 0, QModelIndex())):
-                expanded_categories.append(category.py_name)
+                expanded_categories.append(category.category_key)
             states = [c.tag.state for c in category.child_tags()]
             names = [(c.tag.name, c.tag.category) for c in category.child_tags()]
-            state_map[category.py_name] = dict(izip(names, states))
+            state_map[category.category_key] = dict(izip(names, states))
         return expanded_categories, state_map
 
     def reread_collapse_parameters(self):