diff --git a/addons/im_livechat/static/src/legacy/public_livechat.scss b/addons/im_livechat/static/src/legacy/public_livechat.scss
index 70d0693458a..2368acc9f79 100644
--- a/addons/im_livechat/static/src/legacy/public_livechat.scss
+++ b/addons/im_livechat/static/src/legacy/public_livechat.scss
@@ -83,6 +83,7 @@ $o-mail-thread-window-zindex: $zindex-modal + 1 !default;
         .o_thread_window_title {
             cursor: pointer;
             flex: 1 1 auto;
+            height: 100%;
             @include o-text-overflow;
 
             .o_mail_thread_typing_icon {