diff --git a/src/calibre/gui2/tweak_book/spell.py b/src/calibre/gui2/tweak_book/spell.py
index 665ccf85c6..7d5342b836 100644
--- a/src/calibre/gui2/tweak_book/spell.py
+++ b/src/calibre/gui2/tweak_book/spell.py
@@ -1250,6 +1250,7 @@ class SpellCheck(Dialog):
 
     def show(self):
         Dialog.show(self)
+        self.undo_cache.clear()
         QTimer.singleShot(0, self.refresh)
 
     def accept(self):