When importing WPT tests, the WebKit WPT importer tries to rewrite any URL() reference inside the <style> tags of the ref-tests to fix issues related to moving the ref-test to a new directory. But its currently only doing that for the first URL() reference it finds. Example: 1) WPT test css/css-backgrounds/css-border-radius-002.html has as test reference css/css-backgrounds/reference/css-border-radius-ref-002.html 2) WPT test importer imports css/css-backgrounds/reference/css-border-radius-ref-002.html as css/css-backgrounds/css-border-radius-002-expected.html 3) Since the ref-test has been moved to a different directory, it tries to update relative urls() on the <style> tag: Originally css-border-radius-ref-002.html had: <style type="text/css"> .redSquare { position: absolute; left:50px; width: 100px; height: 100px; background-image:url(../support/yyy.png); } .greenSquare { position: absolute; left:50px; width: 100px; height: 100px; background-image:url(../support/yy.png); } .container { position: absolute; } </style> Therefore, the style on css-border-radius-002-expected.html should have been rewrote as: <style type="text/css"> .redSquare { position: absolute; left:50px; width: 100px; height: 100px; background-image:url(support/yyy.png); } .greenSquare { position: absolute; left:50px; width: 100px; height: 100px; background-image:url(support/yy.png); } .container { position: absolute; } </style> The problem it is currently doing that only for the first URL (yyy.png) but not for the second (yy.png)