diff --git a/index.js b/index.js
index 96a849e..85d1dc7 100644
--- a/index.js
+++ b/index.js
@@ -74,6 +74,8 @@ function loadQuotes() {
 
         // Respond to messages in any room this bot is a member of.
         client.on('Room.timeline', (event, room) => {
+            if (!room) return; // thread timeline events don't carry a room object
+
             const type = event.getType();
             if (type !== 'm.room.message') return;