Webbrowser giving me issues...

[Silo1337]

So I am trying to have a window with Web Browser control in which I will be filling forms on various websites. This is my current code to load google, which works fine:

private void Form1_Load(object sender, EventArgs e){
            WebBrowser1.Navigate("www.google.com");
        }

Then, here's my document completed code:

        private void webBrowser1_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e){

            HtmlDocument doc = this.WebBrowser1.Document;

        }

This is the error I am getting:

Error	1	Cannot implicitly convert type 'object' to 'System.Windows.Forms.HtmlDocument'. An explicit conversion exists (are you missing a cast?)	C:\Users\Admin\AppData\Local\Temporary Projects\WindowsFormsApplication1\Form1.cs	27	32	WindowsFormsApplication1

Can someone please explain to me what I am doing wrong?