--- a/testing/web-platform/meta/MANIFEST.json
+++ b/testing/web-platform/meta/MANIFEST.json
@@ -178112,16 +178112,28 @@
       [
        "/css/vendor-imports/mozilla/mozilla-central-reftests/transforms/containing-block-dynamic-1-ref.html",
        "=="
       ]
      ],
      {}
     ]
    ],
+   "css/vendor-imports/mozilla/mozilla-central-reftests/transforms/perspective-untransformable-no-stacking-context.html": [
+    [
+     "/css/vendor-imports/mozilla/mozilla-central-reftests/transforms/perspective-untransformable-no-stacking-context.html",
+     [
+      [
+       "/css/vendor-imports/mozilla/mozilla-central-reftests/transforms/perspective-untransformable-no-stacking-context-ref.html",
+       "=="
+      ]
+     ],
+     {}
+    ]
+   ],
    "css/vendor-imports/mozilla/mozilla-central-reftests/transforms/perspective-zero-2.html": [
     [
      "/css/vendor-imports/mozilla/mozilla-central-reftests/transforms/perspective-zero-2.html",
      [
       [
        "/css/vendor-imports/mozilla/mozilla-central-reftests/transforms/perspective-zero-2-ref.html",
        "=="
       ]
@@ -273737,16 +273749,21 @@
      {}
     ]
    ],
    "css/vendor-imports/mozilla/mozilla-central-reftests/transforms/individual-transform-2-ref.html": [
     [
      {}
     ]
    ],
+   "css/vendor-imports/mozilla/mozilla-central-reftests/transforms/perspective-untransformable-no-stacking-context-ref.html": [
+    [
+     {}
+    ]
+   ],
    "css/vendor-imports/mozilla/mozilla-central-reftests/transforms/perspective-zero-2-ref.html": [
     [
      {}
     ]
    ],
    "css/vendor-imports/mozilla/mozilla-central-reftests/transforms/reference/green.html": [
     [
      {}
@@ -551970,17 +551987,17 @@
    "b4030a17be4fc25447e3870fbd46520fd8e786f4",
    "support"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/flexbox/flexbox-align-self-vert-rtl-004.xhtml": [
    "437a2f7ff6e786815a9fad26354e5baab777b590",
    "reftest"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/flexbox/flexbox-anonymous-items-001-ref.html": [
-   "034e0ab0215239f057137323feada9b6a8540e50",
+   "88f1d3fd76beb69334a236fd60c4c94ba9a4d437",
    "support"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/flexbox/flexbox-anonymous-items-001.html": [
    "28ef429725a1030f7416886e61cdef834e74f9e4",
    "reftest"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/flexbox/flexbox-baseline-align-self-baseline-horiz-001-ref.html": [
    "2e0cfde4f917f1c3f02c00105158fd634a21b91f",
@@ -557081,16 +557098,24 @@
   "css/vendor-imports/mozilla/mozilla-central-reftests/transforms/perspective-containing-block-dynamic-1a.html": [
    "6a4dd7a18cd9d400fb704eaa8ceb0e63607eb207",
    "reftest"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/transforms/perspective-containing-block-dynamic-1b.html": [
    "1f6e81539cf5a3c3a339e3a69f4c6446688c3cd3",
    "reftest"
   ],
+  "css/vendor-imports/mozilla/mozilla-central-reftests/transforms/perspective-untransformable-no-stacking-context-ref.html": [
+   "af82ff9650987818b6a5a5c3e82386d0fd882325",
+   "support"
+  ],
+  "css/vendor-imports/mozilla/mozilla-central-reftests/transforms/perspective-untransformable-no-stacking-context.html": [
+   "3d2248b6f9200cd23607c1fe6ff543260c43e378",
+   "reftest"
+  ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/transforms/perspective-zero-2-ref.html": [
    "54a7661d6ae90a46a811d988687e2d4b9b927a96",
    "support"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/transforms/perspective-zero-2.html": [
    "08ffb003a59c901710e0a613ee0f89ea506fa035",
    "reftest"
   ],
@@ -557098,17 +557123,17 @@
    "3eae4973f7fb9badf5826c29cce57440a56f92e2",
    "reftest"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/transforms/reference/green.html": [
    "e6c03e1340e293fe4080c1cec52df9f3a39fa2f4",
    "support"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/transforms/reftest.list": [
-   "791816169df64e27949974a29a47805c91592dc5",
+   "56d1d0dca24abcb9a9147b55f10f2a47b5efd61f",
    "support"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/transforms/transform-containing-block-dynamic-1a.html": [
    "e336c1c202f3c31f7146ebe546d8a78e594b7af4",
    "reftest"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/transforms/transform-containing-block-dynamic-1b.html": [
    "ca45ef0280b7743718e22c26e5b5b3eddd7357cf",
@@ -558394,17 +558419,17 @@
    "dd314978ffb94fe9b05a18a5208e5edc1d8dd433",
    "support"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/writing-modes-3/logical-physical-mapping-001.html": [
    "aecb565dbe31fd43ebce9bf6aa48105ecbe43dad",
    "reftest"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/writing-modes-3/reftest.list": [
-   "b9954b5e7f7ae188dc9323e7ae4b29147e80e96c",
+   "30fbc616b8608ca9b5dc1aa1a17a0dc12011ddc0",
    "support"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/writing-modes-3/support/WidthTest-Regular.otf": [
    "0563d8cd8285d76ce45b95f564be09a9ab55fe76",
    "support"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/writing-modes-3/support/tcy.css": [
    "246dcf3e2a6eb06de77b80889b075273ec325127",

--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/flexbox/flexbox-anonymous-items-001-ref.html
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/flexbox/flexbox-anonymous-items-001-ref.html
@@ -5,11 +5,11 @@
 -->
 <html>
 <head>
   <title>CSS Reftest Reference</title>
   <link rel="author" title="Daniel Holbert" href="mailto:dholbert@mozilla.com">
   <meta charset="utf-8">
 </head>
 <body>
-  a ab bx x
+  a a<div style="display:inline-block">b b</div>x x
 </body>
 </html>

new file mode 100644
--- /dev/null
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/transforms/perspective-untransformable-no-stacking-context-ref.html
@@ -0,0 +1,17 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>CSS transforms: 'perspective' on a non-transformable element doesn't create a stacking context</title>
+<link rel="author" title="Matt Woodrow" href="mailto:mwoodrow@mozilla.com">
+<link rel="author" title="Mozilla" href="http://www.mozilla.org/">
+<style>
+  html, body { margin: 0; padding: 0 }
+  #fixedmoves {
+    position: absolute;
+    background: green;
+    height: 100px;
+    width: 100px;
+  }
+</style>
+<body>
+  <div id="fixedmoves"></div>
+</body>

new file mode 100644
--- /dev/null
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/transforms/perspective-untransformable-no-stacking-context.html
@@ -0,0 +1,25 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>CSS transforms: 'perspective' on a non-transformable element doesn't create a stacking context</title>
+<link rel="author" title="Matt Woodrow" href="mailto:mwoodrow@mozilla.com">
+<link rel="author" title="Mozilla" href="http://www.mozilla.org/">
+<link rel="help" href="https://drafts.csswg.org/css-transforms-2/#perspective-property">
+<link rel="match" href="perspective-untransformable-no-stacking-context-ref.html">
+<meta name="assert" content="Perspective on a non-transformable element shouldn't create a stacking context.">
+<style>
+* { margin: 0; padding: 0; }
+div, span { width: 100px; height: 100px }
+#perspective { background: green; padding-top: 100px; perspective: 100px; }
+#child { display:inline-block; z-index: -1; position:absolute; background: red; }
+#spacer { display:inline-block; }
+#wrapper { overflow:hidden }
+</style>
+<body>
+  <div id="wrapper">
+    <span id="perspective">
+      <div id="child">
+      </div>
+      <span id="spacer"></span>
+    </span>
+  </div>
+</body>

--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/transforms/reftest.list
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/transforms/reftest.list
@@ -1,13 +1,14 @@
 == transform-containing-block-dynamic-1a.html containing-block-dynamic-1-ref.html
 == transform-containing-block-dynamic-1b.html containing-block-dynamic-1-ref.html
 == perspective-containing-block-dynamic-1a.html containing-block-dynamic-1-ref.html
 == perspective-containing-block-dynamic-1b.html containing-block-dynamic-1-ref.html
 == perspective-zero.html reference/green.html
 == perspective-zero-2.html perspective-zero-2-ref.html
+== perspective-untransformable-no-stacking-context.html perspective-untransformable-no-stacking-context-ref.html
 
 == individual-transform-1.html individual-transform-1-ref.html
 == individual-transform-2a.html individual-transform-2-ref.html
 == individual-transform-2b.html individual-transform-2-ref.html
 == individual-transform-2c.html individual-transform-2-ref.html
 == individual-transform-2d.html individual-transform-2-ref.html
 == individual-transform-2e.html individual-transform-2-ref.html

--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/writing-modes-3/reftest.list
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/writing-modes-3/reftest.list
@@ -1,9 +1,8 @@
-
 == text-combine-upright-break-inside-001.html text-combine-upright-break-inside-001-ref.html
 == text-combine-upright-break-inside-001a.html text-combine-upright-break-inside-001-ref.html
 == text-combine-upright-compression-001.html text-combine-upright-compression-001-ref.html
 == text-combine-upright-compression-002.html text-combine-upright-compression-002-ref.html
 == text-combine-upright-compression-003.html text-combine-upright-compression-003-ref.html
 == text-combine-upright-compression-004.html text-combine-upright-compression-004-ref.html
 == text-combine-upright-compression-005.html text-combine-upright-compression-005-ref.html
 == text-combine-upright-compression-005a.html text-combine-upright-compression-005-ref.html