diff --git a/hookshot/tinker-tickets.js b/hookshot/tinker-tickets.js
index 47d29bc..ff22829 100644
--- a/hookshot/tinker-tickets.js
+++ b/hookshot/tinker-tickets.js
@@ -77,4 +77,13 @@ if (event === 'ticket_created') {
   html  = '[tinker-tickets] event: <code>' + event + '</code> ticket #' + id;
 }
 
-result = { version: 'v2', plain: plain, html: html, msgtype: 'm.text' };
+// Explicit mentions (m.mentions): from Synapse 1.164 the legacy push rules
+// that pinged on a user ID or display name in the body are off by default
+// (MSC4210), so the people to notify must be listed here.
+result = {
+  version: 'v2',
+  plain: plain,
+  html: html,
+  msgtype: 'm.text',
+  mentions: { user_ids: notifyUsers }
+};
diff --git a/matrixbot/commands.py b/matrixbot/commands.py
index f704069..8490946 100644
--- a/matrixbot/commands.py
+++ b/matrixbot/commands.py
@@ -2273,7 +2273,9 @@ async def cmd_roast(client: AsyncClient, room_id: str, sender: str, args: str):
         f'<blockquote>{roast}</blockquote>'
         f'<sup><em>via {_model_label(CREATIVE_MODEL)}</em></sup>'
     )
-    await send_html(client, room_id, plain, html)
+    # Ping the person being roasted when they were named by Matrix ID.
+    target_id = target_raw if re.fullmatch(r"@[^\s:]+:[^\s]+", target_raw) else None
+    await send_html(client, room_id, plain, html, mention_user_ids=[target_id] if target_id else None)
 
 
 # ---------------------------------------------------------------------------
diff --git a/matrixbot/utils.py b/matrixbot/utils.py
index a7040a2..020a80a 100644
--- a/matrixbot/utils.py
+++ b/matrixbot/utils.py
@@ -70,17 +70,25 @@ async def send_text(client: AsyncClient, room_id: str, text: str):
     return resp
 
 
-async def send_html(client: AsyncClient, room_id: str, plain: str, html: str):
+async def send_html(
+    client: AsyncClient, room_id: str, plain: str, html: str, mention_user_ids: list[str] | None = None
+):
     logger = logging.getLogger("matrixbot")
+    content = {
+        "msgtype": "m.text",
+        "body": plain,
+        "format": "org.matrix.custom.html",
+        "formatted_body": html,
+    }
+    # Explicit mentions (m.mentions). From Synapse 1.164 a name or user ID in
+    # the body no longer pings anyone (MSC4210), so a message that should
+    # notify someone has to say so.
+    if mention_user_ids:
+        content["m.mentions"] = {"user_ids": mention_user_ids}
     resp = await _room_send_trusted(
         client, room_id,
         message_type="m.room.message",
-        content={
-            "msgtype": "m.text",
-            "body": plain,
-            "format": "org.matrix.custom.html",
-            "formatted_body": html,
-        },
+        content=content,
     )
     if not isinstance(resp, RoomSendResponse):
         logger.error("send_html failed: %s", resp)