diff --git a/deluge/ui/web/js/ext-extensions-debug.js b/deluge/ui/web/js/ext-extensions-debug.js
index 91fa5c3ba..1270308f2 100644
--- a/deluge/ui/web/js/ext-extensions-debug.js
+++ b/deluge/ui/web/js/ext-extensions-debug.js
@@ -412,7 +412,7 @@ Ext.extend(Ext.ux.form.Spinner.NumberStrategy, Ext.ux.form.Spinner.Strategy, {
         if(!this.allowDecimals || this.decimalPrecision == -1 || nan || !value){
             return nan ? '' : value;
         }
-        return value.toFixed(this.decimalPrecision);
+        return Number(value).toFixed(this.decimalPrecision);
     }
 });