diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5989289..d64938a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+4.0.1 / 2021-08-20
+==================
+  * Debug version to investigate issue with `js-yaml` & `js-yaml-js-types`
+
 4.0.0 / 2021-07-04
 ==================
   * Dropped support of CoffeeScript **(breaking change)**
diff --git a/lib/readfile.js b/lib/readfile.js
index 2985331..f8b4f73 100644
--- a/lib/readfile.js
+++ b/lib/readfile.js
@@ -14,7 +14,11 @@ module.exports = function(file) {
     if (ext.match(/ya?ml/)) {
         var res = fs.readFileSync(file, 'utf8');
         var yaml = require('js-yaml');
-        var schema = yaml.DEFAULT_SCHEMA.extend(require('js-yaml-js-types').regexp);
+        var REGEXP_TYPE = require('js-yaml-js-types').regexp;
+        if (!(REGEXP_TYPE instanceof yaml.Type)) {
+            console.warn('Invalid js-yaml extension type type:', REGEXP_TYPE);
+        }
+        var schema = yaml.DEFAULT_SCHEMA.extend(REGEXP_TYPE);
         return yaml.load(res, { schema: schema });
     }
 
diff --git a/package.json b/package.json
index 12d4c21..fac8a68 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "load-grunt-config",
-  "version": "4.0.0",
+  "version": "4.0.1",
   "description": "Grunt plugin that lets you break up your Gruntfile config by task",
   "main": "index.js",
   "scripts": {