diff --git a/src/slack/monitor/events/messages.ts b/src/slack/monitor/events/messages.ts
index d63ce780d30..6891b18c3b9 100644
--- a/src/slack/monitor/events/messages.ts
+++ b/src/slack/monitor/events/messages.ts
@@ -102,12 +102,18 @@ export function registerSlackMessageEvents(params: {
   });
   // Slack may dispatch channel/group message subscriptions under typed event
   // names. Register explicit handlers so both delivery styles are supported.
-  ctx.app.event("message.channels", async ({ event, body }: SlackEventMiddlewareArgs) => {
-    await handleIncomingMessageEvent({ event, body });
-  });
-  ctx.app.event("message.groups", async ({ event, body }: SlackEventMiddlewareArgs) => {
-    await handleIncomingMessageEvent({ event, body });
-  });
+  ctx.app.event(
+    "message.channels",
+    async ({ event, body }: SlackEventMiddlewareArgs<"message.channels">) => {
+      await handleIncomingMessageEvent({ event, body });
+    },
+  );
+  ctx.app.event(
+    "message.groups",
+    async ({ event, body }: SlackEventMiddlewareArgs<"message.groups">) => {
+      await handleIncomingMessageEvent({ event, body });
+    },
+  );
 
   ctx.app.event("app_mention", async ({ event, body }: SlackEventMiddlewareArgs<"app_mention">) => {
     try {