diff --git a/addons/mail/static/src/xml/web_kanban_activity.xml b/addons/mail/static/src/xml/web_kanban_activity.xml
index e6d82e3773f..b8480e84ab0 100644
--- a/addons/mail/static/src/xml/web_kanban_activity.xml
+++ b/addons/mail/static/src/xml/web_kanban_activity.xml
@@ -3,7 +3,7 @@
 
 <t t-name="mail.KanbanActivity">
     <div class="o_kanban_inline_block dropdown o_mail_activity">
-        <a class="dropdown-toggle o-no-caret o_activity_btn" data-toggle="dropdown" role="button">
+        <a class="dropdown-toggle o-no-caret o_activity_btn" data-toggle="dropdown" role="button" data-boundary="window">
             <!-- span classes are generated dynamically (see _render) -->
             <span t-att-title="widget.selection[widget.activityState]" role="img" t-att-aria-label="widget.selection[widget.activity_state]"/>
        </a>