ASP.NET database image handler doesn't display ICO image format

I'm storing my images in a sql 2008 database as varbinary(max) and displaying them on my web page using an httphandler. The httphandler does the following:

context.Response.ContentType = dr("Filetype").ToString()
context.Response.BinaryWrite(DirectCast(dr("File"), Byte()))

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where Filetype is the file extension. For example, GIF, JPG, PNG, ICO.

I use the following markup to display the image:

<asp:Image ID="Image1" runat="server" ImageUrl="~/HttpHandlers/DBImageHandler.ashx?fileid=11" />

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The code works fine for PNG but not for ICO. I know the web site can display ICO file extensions since I was originally storing the files on web server disk drive and displaying them normally (ImageUrl='~/images/MyIcon.ico').

Do I need a different content type than ico to display those file types?

Thanks in advance.