diff --git a/src/calibre/gui2/tweak_book/editor/smarts/html.py b/src/calibre/gui2/tweak_book/editor/smarts/html.py
index 9ee63c403c..854774587a 100644
--- a/src/calibre/gui2/tweak_book/editor/smarts/html.py
+++ b/src/calibre/gui2/tweak_book/editor/smarts/html.py
@@ -352,9 +352,12 @@ class Smarts(NullSmarts):
 
     def remove_tag(self, editor):
         editor.highlighter.join()
+        if not self.last_matched_closing_tag and not self.last_matched_tag:
+            return
+        c = editor.textCursor()
+        c.beginEditBlock()
 
         def erase_tag(tag):
-            c = editor.textCursor()
             c.setPosition(tag.start_block.position() + tag.start_offset)
             c.setPosition(tag.end_block.position() + tag.end_offset + 1, c.KeepAnchor)
             c.removeSelectedText()
@@ -363,6 +366,8 @@ class Smarts(NullSmarts):
             erase_tag(self.last_matched_closing_tag)
         if self.last_matched_tag:
             erase_tag(self.last_matched_tag)
+        c.endEditBlock()
+        self.last_matched_tag = self.last_matched_closing_tag = None
 
     def rename_block_tag(self, editor, new_name):
         editor.highlighter.join()