diff --git a/tests/wpt/webgl/meta/conformance/rendering/out-of-bounds-index-buffers.html.ini b/tests/wpt/webgl/meta/conformance/rendering/out-of-bounds-index-buffers.html.ini
index a448c1c1679..3a31658d39f 100644
--- a/tests/wpt/webgl/meta/conformance/rendering/out-of-bounds-index-buffers.html.ini
+++ b/tests/wpt/webgl/meta/conformance/rendering/out-of-bounds-index-buffers.html.ini
@@ -1,4 +1,5 @@
 [out-of-bounds-index-buffers.html]
+  bug: https://github.com/servo/servo/issues/20599
   [WebGL test #2: should be 0,255,0,255\nat (0, 0) expected: 0,255,0,255 was 0,0,255,255]
     expected: FAIL