diff --git a/src/calibre/gui2/tweak_book/editor/smarts/html.py b/src/calibre/gui2/tweak_book/editor/smarts/html.py
index 310bfd2ee7..7ac01e57bd 100644
--- a/src/calibre/gui2/tweak_book/editor/smarts/html.py
+++ b/src/calibre/gui2/tweak_book/editor/smarts/html.py
@@ -275,7 +275,7 @@ def ensure_not_within_tag_definition(cursor, forward=True):
     if boundary.is_start:
         # We are inside a tag
         if forward:
-            block, boundary = next_tag_boundary(block, offset)
+            block, boundary = next_tag_boundary(block, max(0, offset-1))
             if block is not None:
                 cursor.setPosition(block.position() + boundary.offset + 1)
                 return True