diff --git a/addons/mail/static/src/css/mail.css b/addons/mail/static/src/css/mail.css
new file mode 100644
index 00000000000..f50805cd707
--- /dev/null
+++ b/addons/mail/static/src/css/mail.css
@@ -0,0 +1 @@
+/** ThreadView widget **/