diff --git a/src/components/structures/LeftPanel.js b/src/components/structures/LeftPanel.js
index 23dba3dbb5..1988dc5ef9 100644
--- a/src/components/structures/LeftPanel.js
+++ b/src/components/structures/LeftPanel.js
@@ -30,6 +30,8 @@ import VectorConferenceHandler from '../../VectorConferenceHandler';
 var LeftPanel = React.createClass({
     displayName: 'LeftPanel',
 
+    // NB. If you add props, don't forget to update
+    // shouldComponentUpdate!
     propTypes: {
         collapsed: React.PropTypes.bool.isRequired,
     },