diff --git a/control/buttoncontrol.js b/control/buttoncontrol.js
index 24da8730..af01f40b 100644
--- a/control/buttoncontrol.js
+++ b/control/buttoncontrol.js
@@ -2,7 +2,7 @@
released under the CeCILL-B license (French BSD license)
(http://www.cecill.info/licences/Licence_CeCILL-B_V1-en.txt).
*/
-/** A simple button control
+/** A simple push button control
*
* @constructor
* @extends {ol.control.Control}
@@ -14,7 +14,7 @@
*/
ol.control.Button = function(options)
{ options = options || {};
- var element = $("
").addClass(options.className + ' ol-button ol-unselectable ol-control');
+ var element = $("
").addClass((options.className||"") + ' ol-button ol-unselectable ol-control');
var self = this;
$("