diff --git a/src/utils.js b/src/utils.js
index 9dc9e51..2ad6055 100644
--- a/src/utils.js
+++ b/src/utils.js
@@ -41,6 +41,7 @@ export function is_plain_object(thing) {
 	return (
 		proto === Object.prototype ||
 		proto === null ||
+		Object.getPrototypeOf(proto) === null ||
 		Object.getOwnPropertyNames(proto).sort().join('\0') === object_proto_names
 	);
 }
diff --git a/test/test.js b/test/test.js
index ebd4147..87c7ec3 100644
--- a/test/test.js
+++ b/test/test.js
@@ -9,6 +9,12 @@ class Custom {
 	}
 }
 
+const NullObject = (() => {
+  const C = function () {};
+  C.prototype = Object.create(null);
+  return C;
+})()
+
 const node_version = +process.versions.node.split('.')[0];
 
 const fixtures = {
@@ -320,6 +326,21 @@ const fixtures = {
 			};
 		})(Object.create(null)),
 
+		((obj) => {
+			obj.self = obj;
+			return {
+				name: 'Object with null prototype class',
+				value: obj,
+				js: '(function(a){a.foo="bar";a.self=a;return a}({}))',
+				json: '[{"foo":1,"self":0},"bar"]',
+				validate: (value) => {
+					assert.is(value.foo, "bar")
+					assert.is(value.self, value);
+
+				}
+			};
+		})(Object.assign(new NullObject(), { foo: 'bar' })),
+
 		((first, second) => {
 			first.second = second;
 			second.first = first;