diff --git a/lib/index.js b/lib/index.js
index bfcb715..405615d 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -221,3 +221,4 @@ function getSecret(request, secret, token, callback) {
 };
 
 exports.authorize = authorize;
+exports.UnauthorizedError = UnauthorizedError;
diff --git a/package.json b/package.json
index ba5258a..8a8ff41 100644
--- a/package.json
+++ b/package.json
@@ -3,6 +3,7 @@
   "version": "4.5.0",
   "description": "authenticate socket.io connections using JWTs",
   "main": "lib/index.js",
+  "types": "./types/index.d.ts",
   "keywords": [
     "socket",
     "socket.io",
@@ -22,6 +23,7 @@
   },
   "license": "MIT",
   "dependencies": {
+	"@types/socket.io": "~1.4.29",
     "jsonwebtoken": "^5.0.0",
     "xtend": "~2.1.2"
   },
diff --git a/types/index.d.ts b/types/index.d.ts
new file mode 100644
index 0000000..9e6c428
--- /dev/null
+++ b/types/index.d.ts
@@ -0,0 +1,70 @@
+/**
+ * This module allows to authenticate socket.io connections with JWTs.
+ * This is especially if you do not want to use cookies in a single page application.
+ */
+
+/// <reference types="socket.io" />
+
+declare module 'socketio-jwt' {
+
+  /**
+   * Defines possible errors for the secret-callback.
+   */
+  interface ISocketIOError {
+    readonly code: string;
+    readonly message: string;
+  }
+
+  /**
+   * Callback gets called, if secret is given dynamically.
+   */
+  interface ISocketCallback {
+    (err: ISocketIOError, success: string): void;
+  }
+
+  interface ISocketIOMiddleware {
+    (socket: SocketIO.Socket, fn: (err?: any) => void): void;
+  }
+
+  interface IOptions {
+    additional_auth?: (decoded: object, onSuccess: () => void, onError: (err: (string | ISocketIOError), code: string) => void) => void;
+
+    callback?: (false | number);
+    secret: (string | ((request: any, decodedToken: object, callback: ISocketCallback) => void));
+
+    decodedPropertyName?: string;
+    auth_header_required?: boolean;
+    handshake?: boolean;
+    required?: boolean;
+    timeout?: number;
+  }
+
+  function authorize(options: IOptions/*, onConnection: Function*/): ISocketIOMiddleware;
+
+  interface UnauthorizedError extends Error {
+    readonly message: string;
+    readonly inner: object;
+    readonly data: { message: string, code: string, type: 'UnauthorizedError' }
+  }
+
+  var UnauthorizedError: {
+    prototype: UnauthorizedError;
+    new (code: string, error: { message: string }): UnauthorizedError;
+  }
+
+  /**
+   * This is an augmented version of the SocketIO.Server.
+   * It knows the 'authenticated' event and should be extended in future.
+   * @see SocketIO.Server 
+   */
+  export interface JWTServer extends SocketIO.Server {
+
+    /**
+     * The event gets fired when a new connection is authenticated via JWT.
+     * @param event The event being fired: 'authenticated'
+     * @param listener A listener that should take one parameter of type Socket
+     * @return The default '/' Namespace
+     */
+    on(event: ('authenticated' | string), listener: (socket: SocketIO.Socket) => void): SocketIO.Namespace;
+  }
+}