diff --git a/umap/static/umap/js/umap.features.js b/umap/static/umap/js/umap.features.js
index 972454d9..061030f6 100644
--- a/umap/static/umap/js/umap.features.js
+++ b/umap/static/umap/js/umap.features.js
@@ -396,7 +396,8 @@ U.FeatureMixin = {
     const geojson = this.parentClass.prototype.toGeoJSON.call(this)
     geojson.properties = this.cloneProperties()
     geojson.id = this.id
-    geojson.properties._storage_options = undefined
+    // biome-ignore lint/performance/noDelete: we do not want the key at all.
+    delete geojson.properties._storage_options
     return geojson
   },
 
diff --git a/umap/static/umap/js/umap.share.js b/umap/static/umap/js/umap.share.js
index 83013938..567b8fd0 100644
--- a/umap/static/umap/js/umap.share.js
+++ b/umap/static/umap/js/umap.share.js
@@ -21,7 +21,8 @@ U.Share = L.Class.extend({
         map.eachFeature((feature) => {
           const row = feature.toGeoJSON().properties
           const center = feature.getCenter()
-          row._umap_options = undefined
+          // biome-ignore lint/performance/noDelete: we do not want the key at all.
+          delete row._umap_options
           row.Latitude = center.lat
           row.Longitude = center.lng
           table.push(row)