In ASP.Net is there a way to get the alt attribute of server-side image tags to render with an empty value? Preferably without creating a new derived class?

In order to pass accessibility tests, I need to add alt="" to images where they are purely decorative and there is no purpose for text to be read-out by screen readers.

But both of the following result in the alt tag being ommitted, making the image fail the accessibility checks…

<img runat="server" src="~/myimage.jpg" alt="" />
<asp:Image runat="server" ImageUrl="~/myimage.jpg" AlternateText="" />

This is the rendered HTML…

<img src="myimage.jpg" />
<img src="myimage.jpg" style="border-width:0px;" />