diff --git a/addons/calendar/views/calendar_views.xml b/addons/calendar/views/calendar_views.xml
index e8f7734c235..804ff5216b1 100644
--- a/addons/calendar/views/calendar_views.xml
+++ b/addons/calendar/views/calendar_views.xml
@@ -238,7 +238,7 @@
                                     readonly="not user_can_edit"
                                 />
                             </div>
-                            <div class="alert alert-warning o_form_header mt-2" invisible="not invalid_email_partner_ids" role="status">
+                            <div class="alert alert-warning o_form_header mt-2" colspan="2" invisible="not invalid_email_partner_ids" role="status">
                                 <p><strong>The following attendees have invalid email addresses and won't receive any email notifications:</strong></p>
                                 <field name="invalid_email_partner_ids" widget="many2manyattendee" class="oe_inline"/>
                             </div>