diff --git a/empress/support_files/js/side-panel-handler.js b/empress/support_files/js/side-panel-handler.js
index 1002c5dfb..0a7045c14 100644
--- a/empress/support_files/js/side-panel-handler.js
+++ b/empress/support_files/js/side-panel-handler.js
@@ -186,7 +186,7 @@ define(["underscore", "Colorer"], function (_, Colorer) {
         // color tree
         this[colorMethodName]();
 
-        var lWidth = lwInput.value;
+        var lWidth = parseInt(lwInput.value);
         if (lWidth !== 1) {
             this.empress.thickenSameSampleLines(lWidth - 1);
         }