diff --git a/src/index.test.ts b/src/index.test.ts
index a4f247d..68882a9 100644
--- a/src/index.test.ts
+++ b/src/index.test.ts
@@ -2,16 +2,19 @@ import { Failure, fold, Initialized, Pending, Success } from './index';
 
 test('Initialized', () => {
   expect(new Initialized()).toBeInstanceOf(Initialized);
+  expect(new Initialized().kind).toEqual('Initialized');
 });
 
 test('Pending', () => {
   expect(new Pending()).toBeInstanceOf(Pending);
+  expect(new Pending().kind).toEqual('Pending');
 });
 
 test('Success', () => {
   const data = { apple: 'sauce' };
   const state = new Success(data);
   expect(state).toBeInstanceOf(Success);
+  expect(state.kind).toEqual('Success');
   expect(state.data).toEqual(data);
 });
 
@@ -23,6 +26,7 @@ test('Failure', () => {
   const error = 500;
   const state = new Failure(error);
   expect(state).toBeInstanceOf(Failure);
+  expect(state.kind).toEqual('Failure');
   expect(state.error).toEqual(error);
 });
 
diff --git a/src/index.ts b/src/index.ts
index 57c73f6..b3a30e0 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,10 +1,16 @@
 export type RemoteData<D, E> = Initialized | Pending | Success<D> | Failure<E>;
 
-export class Initialized {}
+export class Initialized {
+  private kind = 'Initialized';
+}
 
-export class Pending {}
+export class Pending {
+  private kind = 'Pending';
+}
 
 export class Success<D> {
+  private kind = 'Success';
+
   constructor(public data: D) {
     if (data === null || data === undefined) {
       fail('Parameter "data" is required');
@@ -13,6 +19,8 @@ export class Success<D> {
 }
 
 export class Failure<E> {
+  private kind = 'Failure';
+
   constructor(public error: E) {
     if (error === null || error === undefined) {
       fail('Parameter "error" is required');