diff --git a/src/backend/html_markdown.py b/src/backend/html_markdown.py
index 0817434c..776c965f 100644
--- a/src/backend/html_markdown.py
+++ b/src/backend/html_markdown.py
@@ -119,7 +119,7 @@ class HTMLProcessor:
}
opaque_id = r"[a-zA-Z\d._-]+?"
- user_id_localpart = r"[\x21-\x39\x3D-\x7E]+?"
+ user_id_localpart = r"[\x21-\x39\x3B-\x7E]+?"
user_id_regex = re.compile(
rf"(?P@{user_id_localpart}:(?P[a-zA-Z\d.:-]*[a-zA-Z\d]))",