http://bugs.gentoo.org/344199

--- panel-plugin/libcommon.h
+++ panel-plugin/libcommon.h
@@ -31,6 +31,7 @@
 
 #include <glib.h>
 #include <gtk/gtk.h>
+#include <libxfce4util/libxfce4util.h>
 #include <libxfce4panel/xfce-panel-plugin.h>
 #include "playercontrol_plugin.h"
 #include "playerctrl.h"