diff --git a/tests/ref/basic.list b/tests/ref/basic.list
index 61908f3b0e9..350b75044c8 100644
--- a/tests/ref/basic.list
+++ b/tests/ref/basic.list
@@ -215,7 +215,6 @@ flaky_cpu == linebreak_simple_a.html linebreak_simple_b.html
!= ol_japanese_iroha_bullet_styles.html ol_japanese_iroha_ref.html
== ol_simple_a.html ol_simple_ref.html
== only_child_pseudo_a.html only_child_pseudo_b.html
-== opacity_stacking_context_a.html opacity_stacking_context_ref.html
== outline_offset_a.html outline_offset_ref.html
!= outset_blackborder.html blackborder_ref.html
# Should be == with expected failure. See #2797
diff --git a/tests/wpt/mozilla/meta/MANIFEST.json b/tests/wpt/mozilla/meta/MANIFEST.json
index 1ab064d517e..70e2148e682 100644
--- a/tests/wpt/mozilla/meta/MANIFEST.json
+++ b/tests/wpt/mozilla/meta/MANIFEST.json
@@ -707,6 +707,18 @@
"url": "/_mozilla/css/opacity_simple_a.html"
}
],
+ "css/opacity_stacking_context_a.html": [
+ {
+ "path": "css/opacity_stacking_context_a.html",
+ "references": [
+ [
+ "/_mozilla/css/opacity_stacking_context_ref.html",
+ "=="
+ ]
+ ],
+ "url": "/_mozilla/css/opacity_stacking_context_a.html"
+ }
+ ],
"css/outlines_simple_a.html": [
{
"path": "css/outlines_simple_a.html",
@@ -3492,6 +3504,18 @@
"url": "/_mozilla/css/opacity_simple_a.html"
}
],
+ "css/opacity_stacking_context_a.html": [
+ {
+ "path": "css/opacity_stacking_context_a.html",
+ "references": [
+ [
+ "/_mozilla/css/opacity_stacking_context_ref.html",
+ "=="
+ ]
+ ],
+ "url": "/_mozilla/css/opacity_stacking_context_a.html"
+ }
+ ],
"css/outlines_simple_a.html": [
{
"path": "css/outlines_simple_a.html",
diff --git a/tests/ref/opacity_stacking_context_a.html b/tests/wpt/mozilla/tests/css/opacity_stacking_context_a.html
similarity index 91%
rename from tests/ref/opacity_stacking_context_a.html
rename to tests/wpt/mozilla/tests/css/opacity_stacking_context_a.html
index f108afc4506..7062b7f7acd 100644
--- a/tests/ref/opacity_stacking_context_a.html
+++ b/tests/wpt/mozilla/tests/css/opacity_stacking_context_a.html
@@ -1,6 +1,7 @@
+