diff --git a/layout/reftests/tab-size/reftest.list b/layout/reftests/tab-size/reftest.list
index b45472585fde..478286836d38 100644
--- a/layout/reftests/tab-size/reftest.list
+++ b/layout/reftests/tab-size/reftest.list
@@ -9,3 +9,4 @@
 == tab-size-negative.html     tab-size-initial.html
 == tab-size-change-1a.html     tab-size-change-1-ref.html
 == tab-size-change-1b.html     tab-size-change-1-ref.html
+== tab-size-length.html       tab-size-length-ref.html
diff --git a/layout/reftests/tab-size/tab-size-length-ref.html b/layout/reftests/tab-size/tab-size-length-ref.html
new file mode 100644
index 000000000000..1a1d2a7aa84f
--- /dev/null
+++ b/layout/reftests/tab-size/tab-size-length-ref.html
@@ -0,0 +1,63 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+    <title>CSS Test: Testing the layout of TAB characters with various 'tab-size' length values</title>
+    <link rel="author" title="Mats Palmgren" href="mailto:mats@mozilla.com">
+
+    <meta charset="utf-8">
+    <style type="text/css">
+
+        html,body {
+            color:black; background-color:white; font-size:16px;
+        }
+
+tab { display:inline-block; }
+#t1 tab { width:20px; }
+#t2 tab { width:30px; }
+#t3 tab { width:2ch; }
+#t4 tab { width:3em; }
+#t5 tab { width:calc(10px + 2em); }
+#t6 tab { width:2em; }
+#t7 tab { width:2.5ch; }
+#t8 tab { width:1.6ch; }
+#t9 tab { width:1ch; }
+#t10 tab { width:1ch; }
+#t11 tab { width:1ch; }
+#t12 tab { width:1ch; }
+#t13 tab { width:1ch; }
+#t14 tab { width:1ch; }
+#t15 tab { width:2ch; }
+#t16 tab { width:3ch; }
+#t17 tab { width:3.5ch; }
+
+    </style>
+</head>
+<body>
+
+<pre id="t1"><tab>A</tab><tab>B</tab>C</pre>
+<pre id="t2"><tab>A</tab><tab>B</tab>C</pre>
+<pre id="t3"><tab>A</tab><tab>B</tab>C</pre>
+<pre id="t4"><tab>A</tab><tab>B</tab>C</pre>
+<pre id="t5"><tab>A</tab><tab>B</tab>C</pre>
+<pre id="t6"><tab>A</tab><tab>B</tab>C</pre>
+<pre id="t7"><tab>A</tab><tab>B</tab>C</pre>
+<pre id="t8"><tab>A</tab><tab>B</tab>C</pre>
+<pre id="t9"><tab>A</tab><tab>B</tab>C</pre>
+<pre id="t10"><tab>A</tab><tab>B</tab>C</pre>
+<pre id="t11"><tab>A</tab><tab>B</tab>C</pre>
+<pre id="t12"><tab>A</tab><tab>B</tab>C</pre>
+<pre>A&#9;B&#9;C</pre>
+<pre>A&#9;B&#9;C</pre>
+<pre>A&#9;B&#9;C</pre>
+<pre id="t13"><tab>A</tab><tab>B</tab>C</pre>
+<pre id="t14"><tab>A</tab><tab>B</tab>C</pre>
+<pre id="t15"><tab>A</tab><tab>B</tab>C</pre>
+<pre id="t16"><tab>A</tab><tab>B</tab>C</pre>
+<pre id="t17"><tab>A</tab><tab>B</tab>C</pre>
+<pre>A&#9;B&#9;C</pre>
+
+</body>
+</html>
diff --git a/layout/reftests/tab-size/tab-size-length.html b/layout/reftests/tab-size/tab-size-length.html
new file mode 100644
index 000000000000..5ade0881a521
--- /dev/null
+++ b/layout/reftests/tab-size/tab-size-length.html
@@ -0,0 +1,46 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+    <title>CSS Test: Testing the layout of TAB characters with various 'tab-size' length values</title>
+    <link rel="author" title="Mats Palmgren" href="mailto:mats@mozilla.com">
+    <link rel="help" href="http://www.w3.org/TR/css3-text/#tab-size">
+    <link rel="match" href="tab-size-length-ref.html">
+
+    <meta charset="utf-8">
+    <style type="text/css">
+
+        html,body {
+            color:black; background-color:white; font-size:16px;
+        }
+
+    </style>
+</head>
+<body>
+
+<pre style="-moz-tab-size: 20px">A&#9;B&#9;C</pre>
+<pre style="-moz-tab-size: 30px">A&#9;B&#9;C</pre>
+<pre style="-moz-tab-size: 2ch">A&#9;B&#9;C</pre>
+<pre style="-moz-tab-size: 3em">A&#9;B&#9;C</pre>
+<pre style="-moz-tab-size: calc(10px + 2em)">A&#9;B&#9;C</pre>
+<pre style="-moz-tab-size: calc(2em)">A&#9;B&#9;C</pre>
+<pre style="-moz-tab-size: calc(3.5 - 1)">A&#9;B&#9;C</pre>
+<pre style="-moz-tab-size: 0.8ch">A&#9;B&#9;C</pre>
+<pre style="-moz-tab-size: 0px">A&#9;B&#9;C</pre>
+<pre style="-moz-tab-size: calc(-2em)">A&#9;B&#9;C</pre>
+<pre style="-moz-tab-size: calc(1px - 2px)">A&#9;B&#9;C</pre>
+<pre style="-moz-tab-size: calc(-2.5)">A&#9;B&#9;C</pre>
+<pre style="-moz-tab-size: -2em">A&#9;B&#9;C</pre>
+<pre style="-moz-tab-size: 100%">A&#9;B&#9;C</pre>
+<pre style="-moz-tab-size: calc(10% + 2em)">A&#9;B&#9;C</pre>
+<pre style="-moz-tab-size: 0">A&#9;B&#9;C</pre>
+<pre style="-moz-tab-size: 0.0">A&#9;B&#9;C</pre>
+<pre style="-moz-tab-size: 1">A&#9;B&#9;C</pre>
+<pre style="-moz-tab-size: 3">A&#9;B&#9;C</pre>
+<pre style="-moz-tab-size: 3.5">A&#9;B&#9;C</pre>
+<pre style="-moz-tab-size: -1.5">A&#9;B&#9;C</pre>
+
+</body>
+</html>
