diff --git a/src/components/structures/RoomView.js b/src/components/structures/RoomView.js
index 8e24a75d68..b4735ce0a3 100644
--- a/src/components/structures/RoomView.js
+++ b/src/components/structures/RoomView.js
@@ -917,6 +917,7 @@ module.exports = React.createClass({
         ContentMessages.sendContentToRoom(
             file, this.state.room.roomId, MatrixClientPeg.get(),
         ).done(() => {
+            // Send message_sent callback, for things like _checkIfAlone because after all a file is still a message.
             dis.dispatch({
                 action: 'message_sent',
             });