getImage() treats absolute URL as relative

My site has a page "/en/admin/43/pictures", and on that page there is an img tag with an absolute URL: "/pictures/1/1/200x200.jpg". In the following code, the assertImagePresent() call succeeds, but getImage() fails:

beginAt("/en/admin/43/pictures");
assertImagePresent("/pictures/1/1/200x200.jpg", null);
Image img = getImage("/pictures/1/1/200x200.jpg", null); // AssertionFailedError: Could not load image from http://localhost:8080/en/admin/43/pictures/1/1/200x200.jpg

Looking at the code, I see the problem is in the WebTester.createURL() method, which treats this as a relative URL and tacks it onto the current directory (i.e. /en/admin/43/), giving a nonexistent URL "/en/admin/43/pictures/1/1/200x200.jpg".