diff --git a/tests/ref/basic.list b/tests/ref/basic.list
index 10e4c6b7ed9..8ee7eb74406 100644
--- a/tests/ref/basic.list
+++ b/tests/ref/basic.list
@@ -13,7 +13,6 @@ fragment=top != ../html/acid2.html acid2_ref.html
flaky_cpu == append_style_a.html append_style_b.html
# `?` and `#` in the name is a test for https://github.com/servo/servo/issues/3340
-== iframe/size_attributes.html iframe/size_attributes_ref.html
prefs:"layout.writing-mode.enabled" == iframe/size_attributes_vertical_writing_mode.html iframe/size_attributes_vertical_writing_mode_ref.html
== iframe/stacking_context.html iframe/stacking_context_ref.html
== iframe/stacking_context_position_a.html iframe/stacking_context_position_ref.html
diff --git a/tests/wpt/mozilla/meta/MANIFEST.json b/tests/wpt/mozilla/meta/MANIFEST.json
index 3b6884b2e2d..20221b9b21a 100644
--- a/tests/wpt/mozilla/meta/MANIFEST.json
+++ b/tests/wpt/mozilla/meta/MANIFEST.json
@@ -1759,6 +1759,18 @@
"url": "/_mozilla/css/iframe/simple_inline_width_percentage.html"
}
],
+ "css/iframe/size_attributes.html": [
+ {
+ "path": "css/iframe/size_attributes.html",
+ "references": [
+ [
+ "/_mozilla/css/iframe/size_attributes_ref.html",
+ "=="
+ ]
+ ],
+ "url": "/_mozilla/css/iframe/size_attributes.html"
+ }
+ ],
"css/image_rendering_auto_a.html": [
{
"path": "css/image_rendering_auto_a.html",
@@ -7398,6 +7410,18 @@
"url": "/_mozilla/css/iframe/simple_inline_width_percentage.html"
}
],
+ "css/iframe/size_attributes.html": [
+ {
+ "path": "css/iframe/size_attributes.html",
+ "references": [
+ [
+ "/_mozilla/css/iframe/size_attributes_ref.html",
+ "=="
+ ]
+ ],
+ "url": "/_mozilla/css/iframe/size_attributes.html"
+ }
+ ],
"css/image_rendering_auto_a.html": [
{
"path": "css/image_rendering_auto_a.html",
diff --git a/tests/ref/iframe/size_attributes.html b/tests/wpt/mozilla/tests/css/iframe/size_attributes.html
similarity index 78%
rename from tests/ref/iframe/size_attributes.html
rename to tests/wpt/mozilla/tests/css/iframe/size_attributes.html
index 72e1d1d63d0..48faebca752 100644
--- a/tests/ref/iframe/size_attributes.html
+++ b/tests/wpt/mozilla/tests/css/iframe/size_attributes.html
@@ -1,6 +1,7 @@
+