diff --git a/content/svg/content/test/Makefile.in b/content/svg/content/test/Makefile.in
index 705f50067bf..d45790a1d9f 100644
--- a/content/svg/content/test/Makefile.in
+++ b/content/svg/content/test/Makefile.in
@@ -55,6 +55,7 @@ _TEST_FILES = \
 		test_pathSeg.xhtml \
 		test_scientific.html \
 		scientific-helper.svg \
+		test_length.xhtml \
 		test_text.html \
 		text-helper.svg \
 		test_valueLeaks.xhtml \
diff --git a/content/svg/content/test/test_length.xhtml b/content/svg/content/test/test_length.xhtml
new file mode 100644
index 00000000000..bf7fda285ea
--- /dev/null
+++ b/content/svg/content/test/test_length.xhtml
@@ -0,0 +1,51 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=342513
+-->
+<head>
+  <title>Test SVG Length conversions</title>
+  <script type="text/javascript" src="/MochiKit/packed.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=342513">Mozilla Bug 342513</a>
+<p id="display"></p>
+<div id="content">
+
+  <div width="100%" height="1" id="div">
+  </div>
+  <svg xmlns="http://www.w3.org/2000/svg" width="100%" height="1" id="svg">
+  </svg>
+
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+
+SimpleTest.waitForExplicitFinish();
+
+function run()
+{
+  var svgDoc = document.getElementById('svg');
+  var divElem = document.getElementById('div');
+  var expectedWidth = divElem.clientWidth;
+  // test for the pixel width of the svg
+  is(svgDoc.width.baseVal.value, expectedWidth, 'svgDoc.width.baseVal.value');
+
+  // set the SVG width to ~50% in pixels
+  svgDoc.width.baseVal.newValueSpecifiedUnits(svgDoc.width.baseVal.SVG_LENGTHTYPE_PX, Math.floor(expectedWidth/2));
+  svgDoc.width.baseVal.convertToSpecifiedUnits(svgDoc.width.baseVal.SVG_LENGTHTYPE_PERCENTAGE);
+  // the valueInSpecifiedUnits should now be 50%
+  is(Math.round(svgDoc.width.baseVal.valueInSpecifiedUnits), 50, 'valueInSpecifiedUnits after convertToSpecifiedUnits');
+
+  SimpleTest.finish();
+}
+
+window.addEventListener("load", run, false);
+
+]]>
+</script>
+</pre>
+</body>
+</html>
