diff --git a/modoboa/templates/common/generic_modal.html b/modoboa/templates/common/generic_modal.html
index 373c5ed13..3ff250b34 100644
--- a/modoboa/templates/common/generic_modal.html
+++ b/modoboa/templates/common/generic_modal.html
@@ -3,7 +3,7 @@
 <div class="modal-dialog">
     <div class="modal-content">
         <div class="modal-header">
-          <a class="close" data-dismiss="modal">x</a>
+          <a class="close btn btn-default" data-dismiss="modal">x</a>
           <h3>{{ title }}</h3>
         </div>
         <div class="modal-body">
@@ -11,7 +11,7 @@
         </div>
         <div class="modal-footer">
           {% if action_label %}<a href="#" class="btn btn-primary {{ action_classes }}">{{ action_label }}</a>{% endif %}
-          <a class="btn" data-dismiss="modal">{% trans "Close" %}</a>
+          <a class="btn btn-default" data-dismiss="modal">{% trans "Close" %}</a>
         </div>
     </div><!-- /.modal-content -->
 </div><!-- /.modal-dialog -->