diff --git a/vendor/assets/javascripts/asciinema-player.js b/vendor/assets/javascripts/asciinema-player.js
index 0dbfd7e..a779f69 100644
--- a/vendor/assets/javascripts/asciinema-player.js
+++ b/vendor/assets/javascripts/asciinema-player.js
@@ -352,6 +352,7 @@
   Movie.prototype.start = function(onFrame, onFinish, setTime, setLoading, loop) {
     var timeIntervalId;
 
+    var source = this.source;
     var controller = {};
 
     function onSourceFinish() {
@@ -364,7 +365,7 @@
     }
 
     function start() {
-      var ctrl = this.source.start(onFrame, onSourceFinish, setLoading);
+      var ctrl = source.start(onFrame, onSourceFinish, setLoading);
 
       for (prop in ctrl) {
         controller[prop] = ctrl[prop];