diff --git a/addons/mail/static/src/xml/client_action.xml b/addons/mail/static/src/xml/client_action.xml
index 746082b7fe9..035203e1b61 100644
--- a/addons/mail/static/src/xml/client_action.xml
+++ b/addons/mail/static/src/xml/client_action.xml
@@ -132,7 +132,7 @@
         <div>
             <button type="button" class="btn btn-primary btn-sm o_mail_toggle_channels visible-xs-inline" title="Toggle Channels">Channels</button>
             <button type="button" class="btn btn-primary btn-sm o_mail_chat_button_invite" title="Invite people">Invite</button>
-            <button type="button" class="btn btn-primary btn-sm o_mail_chat_button_mark_read" title="Mark all as read">Mark all read</button>
+            <button type="button" class="btn btn-default btn-sm o_mail_chat_button_mark_read" title="Mark all as read">Mark all read</button>
             <button type="button" class="btn btn-primary btn-sm o_mail_chat_button_unstar_all" title="Unstar all messages">Unstar all</button>
             <button type="button" class="btn btn-default btn-sm o_mail_chat_button_unsubscribe" title="Unsubscribe from channel">Unsubscribe</button>
             <button type="button" class="btn btn-default btn-sm o_mail_chat_button_settings" title="Open channel settings">Settings</button>