diff --git a/layout/reftests/bugs/1384275-1-ref.html b/layout/reftests/bugs/1384275-1-ref.html
new file mode 100644
index 000000000000..bd39590c2633
--- /dev/null
+++ b/layout/reftests/bugs/1384275-1-ref.html
@@ -0,0 +1,5 @@
+<!DOCTYPE html>
+<style>
+p { color: green; }
+</style>
+<p>This text should be green.</p>
diff --git a/layout/reftests/bugs/1384275-1.html b/layout/reftests/bugs/1384275-1.html
new file mode 100644
index 000000000000..a5b12b9991e6
--- /dev/null
+++ b/layout/reftests/bugs/1384275-1.html
@@ -0,0 +1,9 @@
+<!DOCTYPE html>
+<style>
+p { color: red; }
+@import url(https://example.invalid/a.css);
+@supports (color: green) {
+  p { color: green; }
+}
+</style>
+<p>This text should be green.</p>
diff --git a/layout/reftests/bugs/reftest.list b/layout/reftests/bugs/reftest.list
index 4c964d8fbffd..05ce41c658c5 100644
--- a/layout/reftests/bugs/reftest.list
+++ b/layout/reftests/bugs/reftest.list
@@ -2036,3 +2036,4 @@ needs-focus != 1377447-1.html 1377447-2.html
 == 1379696.html 1379696-ref.html
 == 1380224-1.html 1380224-1-ref.html
 == 1384065.html 1384065-ref.html
+== 1384275-1.html 1384275-1-ref.html
