diff --git a/src/components/structures/MessagePanel.js b/src/components/structures/MessagePanel.js
index 6e4697a8f0..f5fa2ceabf 100644
--- a/src/components/structures/MessagePanel.js
+++ b/src/components/structures/MessagePanel.js
@@ -193,7 +193,7 @@ module.exports = React.createClass({
     /**
      * Page up/down.
      *
-     * mult: -1 to page up, +1 to page down
+     * @param {number} mult: -1 to page up, +1 to page down
      */
     scrollRelative: function(mult) {
         if (this.refs.scrollPanel) {
@@ -203,6 +203,8 @@ module.exports = React.createClass({
 
     /**
      * Scroll up/down in response to a scroll key
+     *
+     * @param {KeyboardEvent} ev: the keyboard event to handle
      */
     handleScrollKey: function(ev) {
         if (this.refs.scrollPanel) {
@@ -261,6 +263,7 @@ module.exports = React.createClass({
 
         this.eventNodes = {};
 
+        let visible = false;
         let i;
 
         // first figure out which is the last event in the list which we're
@@ -301,7 +304,7 @@ module.exports = React.createClass({
         // if the readmarker has moved, cancel any active ghost.
         if (this.currentReadMarkerEventId && this.props.readMarkerEventId &&
                 this.props.readMarkerVisible &&
-                this.currentReadMarkerEventId != this.props.readMarkerEventId) {
+                this.currentReadMarkerEventId !== this.props.readMarkerEventId) {
             this.currentGhostEventId = null;
         }
 
@@ -408,8 +411,8 @@ module.exports = React.createClass({
 
             let isVisibleReadMarker = false;
 
-            if (eventId == this.props.readMarkerEventId) {
-                var visible = this.props.readMarkerVisible;
+            if (eventId === this.props.readMarkerEventId) {
+                visible = this.props.readMarkerVisible;
 
                 // if the read marker comes at the end of the timeline (except
                 // for local echoes, which are excluded from RMs, because they
@@ -427,11 +430,11 @@ module.exports = React.createClass({
 
             // XXX: there should be no need for a ghost tile - we should just use a
             // a dispatch (user_activity_end) to start the RM animation.
-            if (eventId == this.currentGhostEventId) {
+            if (eventId === this.currentGhostEventId) {
                 // if we're showing an animation, continue to show it.
                 ret.push(this._getReadMarkerGhostTile());
             } else if (!isVisibleReadMarker &&
-                       eventId == this.currentReadMarkerEventId) {
+                       eventId === this.currentReadMarkerEventId) {
                 // there is currently a read-up-to marker at this point, but no
                 // more. Show an animation of it disappearing.
                 ret.push(this._getReadMarkerGhostTile());
@@ -498,7 +501,7 @@ module.exports = React.createClass({
         }
 
         const eventId = mxEv.getId();
-        const highlight = (eventId == this.props.highlightedEventId);
+        const highlight = (eventId === this.props.highlightedEventId);
 
         // we can't use local echoes as scroll tokens, because their event IDs change.
         // Local echos have a send "status".
@@ -637,7 +640,8 @@ module.exports = React.createClass({
     render: function() {
         const ScrollPanel = sdk.getComponent("structures.ScrollPanel");
         const Spinner = sdk.getComponent("elements.Spinner");
-        let topSpinner, bottomSpinner;
+        let topSpinner;
+        let bottomSpinner;
         if (this.props.backPaginating) {
             topSpinner = <li key="_topSpinner"><Spinner /></li>;
         }