diff --git a/src/Header.js b/src/Header.js
index 8875fa1..ade46b2 100644
--- a/src/Header.js
+++ b/src/Header.js
@@ -71,7 +71,7 @@ function Header(calendar, options) {
 							var icon = options.theme ? smartProperty(options.buttonIcons, buttonName) : null; // why are we using smartProperty here?
 							var text = smartProperty(options.buttonText, buttonName); // why are we using smartProperty here?
 							var button = $(
-								"<span class='fc-button fc-button-" + buttonName + " " + tm + "-state-default'>" +
+								"<span class='fc-button "+(tm == 'ui' ? 'ui-button' : '')+" fc-button-" + buttonName + " " + tm + "-state-default'>" +
 									"<span class='fc-button-inner'>" +
 										"<span class='fc-button-content'>" +
 											(icon ?