diff --git a/src/backend/html_markdown.py b/src/backend/html_markdown.py
index 596f5ff2..01283861 100644
--- a/src/backend/html_markdown.py
+++ b/src/backend/html_markdown.py
@@ -268,7 +268,7 @@ class HTMLProcessor:
 		return {
 			"tags": inline_tags if inline else all_tags,
 			"attributes": inlines_attributes if inline else attributes,
-			"empty": {} if inline else {"hr", "br", "img"},
+			"empty": set() if inline else {"hr", "br", "img"},
 			"separate": {"a"} if inline else {
 				"a", "p", "li", "table", "tr", "th", "td", "br", "hr", "img",
 			},