diff --git a/src/calibre/gui2/tweak_book/boss.py b/src/calibre/gui2/tweak_book/boss.py
index b39b7ffd53..bccc4cec13 100644
--- a/src/calibre/gui2/tweak_book/boss.py
+++ b/src/calibre/gui2/tweak_book/boss.py
@@ -291,9 +291,7 @@ class Boss(QObject):
         editor = editors.get(name, None)
         if editor is None:
             editor = editors[name] = editor_from_syntax(syntax, self.gui.editor_tabs)
-            c = current_container()
-            with c.open(name) as f:
-                data = c.decode(f.read())
+            data = current_container().raw_data(name)
             self.init_editor(name, editor, data)
         self.show_editor(name)