diff --git a/types/websocket/index.d.ts b/types/websocket/index.d.ts
index cd17039b1c..0a15be7d69 100644
--- a/types/websocket/index.d.ts
+++ b/types/websocket/index.d.ts
@@ -679,9 +679,11 @@ declare class w3cwebsocket {
     url: string;
     readyState: number;
     protocol?: string;
-    extenstions: IExtension[];
+    extensions: IExtension[];
     bufferedAmount: number;
 
+    binaryType: "arraybuffer";
+
     CONNECTING: number;
     OPEN: number;
     CLOSING: number;
@@ -692,7 +694,7 @@ declare class w3cwebsocket {
     onclose: () => void;
     onmessage: (message: any) => void;
 
-    constructor(url: string, protocols?: string[], origin?: string, headers?: any[], requestOptions?: object, clientConfig?: IClientConfig);
+    constructor(url: string, protocols?: string | string[], origin?: string, headers?: any[], requestOptions?: object, clientConfig?: IClientConfig);
 
     send(data: Buffer): void;
     send(data: IStringified): void;