diff --git a/src/components/views/elements/TagTile.js b/src/components/views/elements/TagTile.js
index 9bad02e37d..b5dfce72c0 100644
--- a/src/components/views/elements/TagTile.js
+++ b/src/components/views/elements/TagTile.js
@@ -28,6 +28,7 @@ export default React.createClass({
     displayName: 'TagTile',
 
     propTypes: {
+        // A string tag such as "m.favourite" or a group ID such as "+groupid:domain.bla"
         tag: PropTypes.string,
     },