diff --git a/src/calibre/gui2/tweak_book/editor/text.py b/src/calibre/gui2/tweak_book/editor/text.py
index 24bea37bce..da0ea747f8 100644
--- a/src/calibre/gui2/tweak_book/editor/text.py
+++ b/src/calibre/gui2/tweak_book/editor/text.py
@@ -660,6 +660,10 @@ class TextEdit(PlainTextEdit):
             if self.replace_possible_unicode_sequence():
                 ev.accept()
                 return
+        if ev.key() == Qt.Key_Insert:
+            self.setOverwriteMode(self.overwriteMode() ^ True)
+            ev.accept()
+            return
         QPlainTextEdit.keyPressEvent(self, ev)
         if (ev.key() == Qt.Key_Semicolon or ';' in unicode(ev.text())) and tprefs['replace_entities_as_typed'] and self.syntax == 'html':
             self.replace_possible_entity()