diff --git a/addons/mail/static/src/css/mail.css b/addons/mail/static/src/css/mail.css
index 8085d17856c..9c4fc416123 100644
--- a/addons/mail/static/src/css/mail.css
+++ b/addons/mail/static/src/css/mail.css
@@ -27,6 +27,15 @@
     padding: 2px;
 }
 
+.oe_mail_thread_subthread div.oe_mail_thread_act .oe_mail_msg_image, .oe_mail_thread_subthread div.oe_mail_thread_display .oe_mail_msg_image {
+    width: 30px;
+    height: 30px;
+}
+
+.oe_mail_thread_subthread .oe_mail_msg_content, .oe_mail_thread_subthread .oe_mail_msg_content {
+    margin-left: 40px;
+}
+
 .oe_mail_wall_more {
     text-align: center;
 }