diff --git a/umap/static/umap/js/umap.js b/umap/static/umap/js/umap.js
index c8f0d18a..50842862 100644
--- a/umap/static/umap/js/umap.js
+++ b/umap/static/umap/js/umap.js
@@ -1763,7 +1763,7 @@ L.U.Map.include({
       )
       if (this.options.facetKey) {
         L.DomUtil.createButton(
-          'umap-open-filter-link',
+          'umap-open-filter-link flat',
           container,
           ` | ${L._('Select data')}`,
           this.openFacet,