diff --git a/tests/wpt/mozilla/meta/MANIFEST.json b/tests/wpt/mozilla/meta/MANIFEST.json
index 98dbd60fcbb..7da1322edce 100644
--- a/tests/wpt/mozilla/meta/MANIFEST.json
+++ b/tests/wpt/mozilla/meta/MANIFEST.json
@@ -8750,6 +8750,18 @@
             "url": "/_mozilla/mozilla/node_replaceChild.html"
           }
         ],
+        "mozilla/out-of-order-stylesheet-loads-and-imports.html": [
+          {
+            "path": "mozilla/out-of-order-stylesheet-loads-and-imports.html",
+            "url": "/_mozilla/mozilla/out-of-order-stylesheet-loads-and-imports.html"
+          }
+        ],
+        "mozilla/out-of-order-stylesheet-loads.html": [
+          {
+            "path": "mozilla/out-of-order-stylesheet-loads.html",
+            "url": "/_mozilla/mozilla/out-of-order-stylesheet-loads.html"
+          }
+        ],
         "mozilla/parentNode_querySelector.html": [
           {
             "path": "mozilla/parentNode_querySelector.html",
diff --git a/tests/wpt/mozilla/tests/mozilla/out-of-order-stylesheet-loads-and-imports.html b/tests/wpt/mozilla/tests/mozilla/out-of-order-stylesheet-loads-and-imports.html
new file mode 100644
index 00000000000..d22ae59c689
--- /dev/null
+++ b/tests/wpt/mozilla/tests/mozilla/out-of-order-stylesheet-loads-and-imports.html
@@ -0,0 +1,18 @@
+<!doctype html>
+<meta charset="utf-8">
+<title>Out-of-order stylesheet loads for the same element happen correctly, even with imports (issue #15101)</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+async_test(function(t) {
+  var link = document.createElement("link");
+  link.rel = "stylesheet";
+  link.href = "resources/imports-background-red.css?pipe=trickle(d3)";
+  document.head.appendChild(link);
+  link.href = "resources/imports-background-green.css";
+  t.step_timeout(function() {
+    assert_equals(getComputedStyle(document.body).getPropertyValue("background-color"), "rgb(0, 128, 0)");
+    t.done();
+  }, 4000);
+}, "out-of-order stylesheet loads for the same element happen correctly, even with imports");
+</script>
diff --git a/tests/wpt/mozilla/tests/mozilla/out-of-order-stylesheet-loads.html b/tests/wpt/mozilla/tests/mozilla/out-of-order-stylesheet-loads.html
new file mode 100644
index 00000000000..0ed15447bc1
--- /dev/null
+++ b/tests/wpt/mozilla/tests/mozilla/out-of-order-stylesheet-loads.html
@@ -0,0 +1,18 @@
+<!doctype html>
+<meta charset="utf-8">
+<title>Out-of-order stylesheet loads for the same element happen correctly (issue #15101)</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+async_test(function(t) {
+  var link = document.createElement("link");
+  link.rel = "stylesheet";
+  link.href = "resources/background-red.css?pipe=trickle(d3)";
+  document.head.appendChild(link);
+  link.href = "resources/background-green.css";
+  t.step_timeout(function() {
+    assert_equals(getComputedStyle(document.body).getPropertyValue("background-color"), "rgb(0, 128, 0)");
+    t.done();
+  }, 4000);
+}, "out-of-order stylesheet loads for the same element happen correctly");
+</script>
diff --git a/tests/wpt/mozilla/tests/mozilla/resources/background-green.css b/tests/wpt/mozilla/tests/mozilla/resources/background-green.css
new file mode 100644
index 00000000000..9d9d772fb46
--- /dev/null
+++ b/tests/wpt/mozilla/tests/mozilla/resources/background-green.css
@@ -0,0 +1,3 @@
+body {
+  background-color: green;
+}
diff --git a/tests/wpt/mozilla/tests/mozilla/resources/background-red.css b/tests/wpt/mozilla/tests/mozilla/resources/background-red.css
new file mode 100644
index 00000000000..aa1634c2550
--- /dev/null
+++ b/tests/wpt/mozilla/tests/mozilla/resources/background-red.css
@@ -0,0 +1,3 @@
+body {
+  background-color: red;
+}
diff --git a/tests/wpt/mozilla/tests/mozilla/resources/imports-background-green.css b/tests/wpt/mozilla/tests/mozilla/resources/imports-background-green.css
new file mode 100644
index 00000000000..5d5cb67763d
--- /dev/null
+++ b/tests/wpt/mozilla/tests/mozilla/resources/imports-background-green.css
@@ -0,0 +1 @@
+@import url("background-green.css");
diff --git a/tests/wpt/mozilla/tests/mozilla/resources/imports-background-red.css b/tests/wpt/mozilla/tests/mozilla/resources/imports-background-red.css
new file mode 100644
index 00000000000..c7f68081044
--- /dev/null
+++ b/tests/wpt/mozilla/tests/mozilla/resources/imports-background-red.css
@@ -0,0 +1 @@
+@import url("background-red.css");
