diff --git a/addons/mail/static/src/scss/discuss.scss b/addons/mail/static/src/scss/discuss.scss
index 3be85aa013f..0c76829d732 100644
--- a/addons/mail/static/src/scss/discuss.scss
+++ b/addons/mail/static/src/scss/discuss.scss
@@ -110,6 +110,7 @@
         }
 
         .o_mail_thread {
+            position: relative;
             flex: 1 0 0;
             overflow: auto;
             -webkit-overflow-scrolling: touch; // smooth scrolling in iOS app (Safari)