diff --git a/libraries/left.js b/libraries/left.js
index 6491b0c50..4f4daa6c9 100644
--- a/libraries/left.js
+++ b/libraries/left.js
@@ -24,9 +24,9 @@
 var isExpanded   = false;
 
 var imgOpened    = new Image(9,9);
-imgOpened.src    = 'images/minus.gif';
+imgOpened.src    = 'images/minus.png';
 var imgClosed    = new Image(9,9);
-imgClosed.src    = 'images/plus.gif';
+imgClosed.src    = 'images/plus.png';
 
 
 /**