diff --git a/tests/wpt/mozilla/meta/MANIFEST.json b/tests/wpt/mozilla/meta/MANIFEST.json
index 391b2f83b8b..5f70f04ee64 100644
--- a/tests/wpt/mozilla/meta/MANIFEST.json
+++ b/tests/wpt/mozilla/meta/MANIFEST.json
@@ -19874,6 +19874,12 @@
      {}
     ]
    ],
+   "mozilla/unitless-length.html": [
+    [
+     "/_mozilla/mozilla/unitless-length.html",
+     {}
+    ]
+   ],
    "mozilla/variadic-interface.html": [
     [
      "/_mozilla/mozilla/variadic-interface.html",
@@ -31497,6 +31503,10 @@
    "47ee847e660eb907a7bd916cf37cf3ceba68ea7d",
    "testharness"
   ],
+  "mozilla/unitless-length.html": [
+   "dfb31d3f9c4f24913055924c375f08b990b63e49",
+   "testharness"
+  ],
   "mozilla/variadic-interface.html": [
    "9edd5150d36fabae42077a034655a8457eb75bff",
    "testharness"
diff --git a/tests/wpt/mozilla/tests/mozilla/unitless-length.html b/tests/wpt/mozilla/tests/mozilla/unitless-length.html
new file mode 100644
index 00000000000..a79520844db
--- /dev/null
+++ b/tests/wpt/mozilla/tests/mozilla/unitless-length.html
@@ -0,0 +1,219 @@
+<!doctype html>
+<html>
+ <head>
+  <title>The unitless length quirk</title>
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+  <style> iframe { width:20px; height:20px; } </style>
+ </head>
+ <body>
+  <div id=log></div>
+  <iframe id=quirks></iframe>
+  <iframe id=almost></iframe>
+  <iframe id=standards></iframe>
+  <script>
+    setup({explicit_done:true});
+    onload = function() {
+        var html = "<style id=style></style><div id=test></div><div id=ref></div>";
+        var a_doctype = '<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">';
+        var s_doctype = '<!DOCTYPE HTML>';
+        var q = document.getElementById('quirks').contentWindow;
+        var a = document.getElementById('almost').contentWindow;
+        var s = document.getElementById('standards').contentWindow;
+        q.document.open();
+        q.document.write(html);
+        q.document.close();
+        a.document.open();
+        a.document.write(a_doctype + html);
+        a.document.close();
+        s.document.open();
+        s.document.write(s_doctype + html);
+        s.document.close();
+        [q, a, s].forEach(function(win) {
+            ['style', 'test', 'ref'].forEach(function(id) {
+                win[id] = win.document.getElementById(id);
+            });
+        });
+
+        var tests = [
+        {input:"1", q:"1px"},
+        {input:"+1", q:"1px"},
+        {input:"-1", q:"-1px"},
+        {input:"1.5", q:"1.5px"},
+        {input:"+1.5", q:"1.5px"},
+        {input:"-1.5", q:"-1.5px"},
+        {input:"\\31 "},
+        {input:"+\\31 "},
+        {input:"-\\31 "},
+        {input:"\\31 .5"},
+        {input:"+\\31 .5"},
+        {input:"-\\31 .5"},
+        {input:"1\\31 "},
+        {input:"+1\\31 "},
+        {input:"-1\\31 "},
+        {input:"1\\31 .5"},
+        {input:"+1\\31 .5"},
+        {input:"-1\\31 .5"},
+        {input:"a"},
+        {input:"A"},
+        {input:"1a"},
+        {input:"+1a"},
+        {input:"-1a"},
+        {input:"+1A"},
+        {input:"-1A"},
+        {input:"+a"},
+        {input:"-a"},
+        {input:"+A"},
+        {input:"-A"},
+        {input:"@a"},
+        {input:"@1"},
+        {input:"@1a"},
+        {input:'"a"'},
+        {input:'"1"'},
+        {input:'"1a"'},
+        {input:"url(1)"},
+        {input:"url('1')"},
+        {input:"#1"},
+        {input:"#01"},
+        {input:"#001"},
+        {input:"#0001"},
+        {input:"#00001"},
+        {input:"#000001"},
+        {input:"+/**/1"},
+        {input:"-/**/1"},
+        {input:"calc(1)"},
+        {input:"calc(2 * 2px)", q:"4px", s:"4px"},
+        {input:"1px 2", q:"1px 2px", shorthand:true},
+        {input:"1 2px", q:"1px 2px", shorthand:true},
+        {input:"1px calc(2)", shorthand:true},
+        {input:"calc(1) 2px", shorthand:true},
+        {input:"1 +2", q:"1px 2px", shorthand:true},
+        {input:"1 -2", q:"1px -2px", shorthand:true},
+        ];
+
+        var props = [
+        {prop:'background-position', check:'background-position', check_also:[]},
+        {prop:'border-spacing', check:'border-spacing', check_also:[]},
+        {prop:'border-top-width', check:'border-top-width'},
+        {prop:'border-right-width', check:'border-right-width'},
+        {prop:'border-bottom-width', check:'border-bottom-width'},
+        {prop:'border-left-width', check:'border-left-width'},
+        {prop:'border-width', check:'border-top-width', check_also:['border-right-width', 'border-bottom-width', 'border-left-width']},
+        // {prop:'bottom', check:'bottom'},
+        {prop:'clip', check:'clip'},
+        {prop:'font-size', check:'font-size'},
+        {prop:'height', check:'height'},
+        {prop:'left', check:'left'},
+        {prop:'letter-spacing', check:'letter-spacing'},
+        {prop:'margin-right', check:'margin-right'},
+        {prop:'margin-left', check:'margin-left'},
+        {prop:'margin-top', check:'margin-top'},
+        {prop:'margin-bottom', check:'margin-bottom'},
+        {prop:'margin', check:'margin-top', check_also:['margin-right', 'margin-bottom', 'margin-left']},
+        {prop:'max-height', check:'max-height'},
+        {prop:'max-width', check:'max-width'},
+        {prop:'min-height', check:'min-height'},
+        {prop:'min-width', check:'min-width'},
+        {prop:'padding-top', check:'padding-top'},
+        {prop:'padding-right', check:'padding-right'},
+        {prop:'padding-bottom', check:'padding-bottom'},
+        {prop:'padding-left', check:'padding-left'},
+        {prop:'padding', check:'padding-top', check_also:['padding-right', 'padding-bottom', 'padding-left']},
+        {prop:'right', check:'right'},
+        {prop:'text-indent', check:'text-indent'},
+        // {prop:'top', check:'top'},
+        {prop:'vertical-align', check:'vertical-align'},
+        {prop:'width', check:'width'},
+        {prop:'word-spacing', check:'word-spacing'},
+        ];
+        var style_template = '#test{border-style:solid;position:relative;{prop}:{test};}' +
+                             '#ref{border-style:solid;position:relative;{prop}:{ref};}';
+
+        tests.forEach(function(t) {
+            for (var i in props) {
+                if (t.shorthand && !(props[i].check_also)) {
+                    continue;
+                }
+                test(function() {
+                    q.style.textContent = style_template.replace('{test}', t.input)
+                                .replace('{ref}', t.q).replace(/\{prop\}/g, props[i].prop)
+                                .replace(/clip:[^;]+/g, function(match) {
+                                    return 'clip:rect(auto, auto, auto, ' + match.substr(5) + ')';
+                                });
+                    assert_equals(q.getComputedStyle(q.test).getPropertyValue(props[i].check),
+                                  q.getComputedStyle(q.ref).getPropertyValue(props[i].check),
+                                  props[i].prop);
+                    if (t.shorthand && props[i].check_also) {
+                        for (var j in props[i].check_also) {
+                            assert_equals(q.getComputedStyle(q.test).getPropertyValue(props[i].check_also[j]),
+                                          q.getComputedStyle(q.ref).getPropertyValue(props[i].check_also[j]),
+                                          props[i].prop + ', checking ' + props[i].check_also[j]);
+                        }
+                    }
+                }, props[i].prop + ": " + t.input + ' (quirks)');
+                test(function() {
+                    a.style.textContent = style_template.replace('{test}', t.input)
+                                .replace('{ref}', t.s).replace(/\{prop\}/g, props[i].prop)
+                                .replace(/clip:[^;]+/g, function(match) {
+                                    return 'clip:rect(auto, auto, auto, ' + match.substr(5) + ')';
+                                });
+                    assert_equals(a.getComputedStyle(a.test).getPropertyValue(props[i].check),
+                                  a.getComputedStyle(a.ref).getPropertyValue(props[i].check),
+                                  props[i].prop + ' in almost standards mode');
+                    if (t.shorthand && props[i].check_also) {
+                        for (var j in props[i].check_also) {
+                            assert_equals(a.getComputedStyle(a.test).getPropertyValue(props[i].check_also[j]),
+                                          a.getComputedStyle(a.ref).getPropertyValue(props[i].check_also[j]),
+                                          props[i].prop + ', checking ' + props[i].check_also[j]);
+                        }
+                    }
+                }, props[i].prop + ": " + t.input + ' (almost standards)');
+                test(function() {
+                    s.style.textContent = style_template.replace('{test}', t.input)
+                                .replace('{ref}', t.s).replace(/\{prop\}/g, props[i].prop)
+                                .replace(/clip:[^;]+/g, function(match) {
+                                    return 'clip:rect(auto, auto, auto, ' + match.substr(5) + ')';
+                                });
+                    assert_equals(s.getComputedStyle(s.test).getPropertyValue(props[i].check),
+                                  s.getComputedStyle(s.ref).getPropertyValue(props[i].check),
+                                  props[i].prop + ' in standards mode');
+                    if (t.shorthand && props[i].check_also) {
+                        for (var j in props[i].check_also) {
+                            assert_equals(s.getComputedStyle(s.test).getPropertyValue(props[i].check_also[j]),
+                                          s.getComputedStyle(s.ref).getPropertyValue(props[i].check_also[j]),
+                                          props[i].prop + ', checking ' + props[i].check_also[j]);
+                        }
+                    }
+                }, props[i].prop + ": " + t.input + ' (standards)');
+            }
+        });
+
+        var other_tests = [
+        {input:'background:1 1', prop:'background-position'},
+        {input:'border-top:red solid 1', prop:'border-top-width'},
+        {input:'border-right:red solid 1', prop:'border-right-width'},
+        {input:'border-bottom:red solid 1', prop:'border-bottom-width'},
+        {input:'border-left:red solid 1', prop:'border-left-width'},
+        {input:'border:red solid 1', prop:'border-top-width'},
+        {input:'font:normal normal normal 40 sans-serif', prop:'font-size'},
+        {input:'outline:red solid 1', prop:'outline-width'},
+        {input:'outline-width:1', prop:'outline-width'},
+        ];
+
+        var other_template = "#test{position:relative;outline-style:solid;{test}}" +
+                             "#ref{outline-style:solid}";
+
+        other_tests.forEach(function(t) {
+            test(function() {
+                q.style.textContent = other_template.replace('{test}', t.input);
+                assert_equals(q.getComputedStyle(q.test).getPropertyValue(t.prop),
+                              q.getComputedStyle(q.ref).getPropertyValue(t.prop),
+                              'quirk was supported');
+            }, 'Excluded property '+t.input);
+        });
+
+        done();
+    }
+  </script>
+ </body>
+</html>
