diff --git a/umap/static/umap/js/umap.core.js b/umap/static/umap/js/umap.core.js
index a9398945..fbbbd901 100644
--- a/umap/static/umap/js/umap.core.js
+++ b/umap/static/umap/js/umap.core.js
@@ -161,7 +161,7 @@ L.Util.detectFileType = (f) => {
 }
 
 L.Util.usableOption = (options, option) =>
-  options[option] !== undefined && options[option] !== ''
+  options[option] !== undefined && options[option] !== '' && options[option] !== null
 
 L.Util.greedyTemplate = (str, data, ignore) => {
   function getValue(data, path) {
diff --git a/umap/static/umap/js/umap.features.js b/umap/static/umap/js/umap.features.js
index a548f3a5..76cbdb7f 100644
--- a/umap/static/umap/js/umap.features.js
+++ b/umap/static/umap/js/umap.features.js
@@ -828,7 +828,7 @@ L.U.PathMixin = {
 
   highlightPath: function () {
     this.parentClass.prototype.setStyle.call(this, {
-      fillOpacity: Math.sqrt(this.getDynamicOption('fillOpacity')),
+      fillOpacity: Math.sqrt(this.getDynamicOption('fillOpacity', 1.0)),
       opacity: 1.0,
       weight: 1.3 * this.getDynamicOption('weight'),
     })
diff --git a/umap/static/umap/test/Feature.js b/umap/static/umap/test/Feature.js
index 7ef10051..688e10e5 100644
--- a/umap/static/umap/test/Feature.js
+++ b/umap/static/umap/test/Feature.js
@@ -244,6 +244,12 @@ describe('L.U.FeatureMixin', function () {
       var path = qs('path[stroke-opacity="1"]')
       assert.ok(path)
     })
+
+    it('should highlight polygon', function () {
+      var path = qs('path[fill="DarkBlue"]')
+      happen.click(path)
+      assert.isAbove(path.attributes['fill-opacity'].value, 0.5)
+    })
   })
 
   describe('#tooltip', function () {