diff --git a/invenio_theme_tugraz/assets/semantic-ui/less/invenio_theme_tugraz/header.less b/invenio_theme_tugraz/assets/semantic-ui/less/invenio_theme_tugraz/header.less
index 98948af..fa29e38 100644
--- a/invenio_theme_tugraz/assets/semantic-ui/less/invenio_theme_tugraz/header.less
+++ b/invenio_theme_tugraz/assets/semantic-ui/less/invenio_theme_tugraz/header.less
@@ -187,6 +187,7 @@ svg:not(:root) {
 .main-menu-underline-line {
   border: 2px solid @greyLight !important;
   border-radius: 0;
+  background-color: @greyLight;
 }
 
 #margin-divider{