diff --git a/layout/style/test/mochitest.ini b/layout/style/test/mochitest.ini
index 58bcecc394f0..5b0427fc36fa 100644
--- a/layout/style/test/mochitest.ini
+++ b/layout/style/test/mochitest.ini
@@ -288,7 +288,6 @@ skip-if = !stylo
 [test_transitions_and_reframes.html]
 [test_transitions_and_restyles.html]
 [test_transitions_and_zoom.html]
-[test_transitions_at_start.html]
 [test_transitions_cancel_near_end.html]
 [test_transitions_computed_values.html]
 [test_transitions_computed_value_combinations.html]
diff --git a/layout/style/test/test_transitions_at_start.html b/layout/style/test/test_transitions_at_start.html
deleted file mode 100644
index 15805bbc090b..000000000000
--- a/layout/style/test/test_transitions_at_start.html
+++ /dev/null
@@ -1,38 +0,0 @@
-<!doctype html>
-<html>
-<!--
-https://bugzilla.mozilla.org/show_bug.cgi?id=1380133
--->
-<head>
-  <meta charset=utf-8>
-  <title>Test for transition value at start (Bug 1380133)</title>
-  <script src="/resources/testharness.js"></script>
-  <script src="/resources/testharnessreport.js"></script>
-  <link rel="stylesheet" href="/resources/testharness.css">
-  <style>
-    a {
-      color: red;
-      transition: 100s color;
-    }
-    a.active {
-      color: blue;
-    }
-  </style>
-</head>
-<body>
-<a id=anchor><span id=span>Test</span></a>
-</body>
-<script>
-'use strict';
-
-const anchor = document.getElementById('anchor');
-const span   = document.getElementById('span');
-
-test(() => {
-  anchor.classList.add('active');
-  assert_equals(getComputedStyle(span).color, 'rgb(255, 0, 0)',
-                'The child of a transitioning element should inherit its'
-                + ' parent\'s transition start value');
-}, 'Transition start value should be inherited');
-</script>
-</html>
