diff --git a/tests/wpt/metadata-css/css21_dev/html4/c5525-fltblck-000.htm.ini b/tests/wpt/metadata-css/css21_dev/html4/c5525-fltblck-000.htm.ini
index 560da0512ec..d3a34f8e2d4 100644
--- a/tests/wpt/metadata-css/css21_dev/html4/c5525-fltblck-000.htm.ini
+++ b/tests/wpt/metadata-css/css21_dev/html4/c5525-fltblck-000.htm.ini
@@ -1,4 +1,4 @@
 [c5525-fltblck-000.htm]
   type: reftest
-  expected:
-    if os == "mac": FAIL
+  disabled:
+    if os == "mac": https://github.com/servo/servo/issues/13920