diff --git a/mozilla/content/base/src/nsPlainTextSerializer.cpp b/mozilla/content/base/src/nsPlainTextSerializer.cpp
index c62529a923f..67236f82c3a 100644
--- a/mozilla/content/base/src/nsPlainTextSerializer.cpp
+++ b/mozilla/content/base/src/nsPlainTextSerializer.cpp
@@ -1070,8 +1070,10 @@ nsPlainTextSerializer::DoAddLeaf(const nsIParserNode *aNode, PRInt32 aTag,
     // Read more in bug 31994.
     return NS_OK;
   }
-  else if (mTagStackIndex > 0 && mTagStack[mTagStackIndex-1] == eHTMLTag_script) {
-    // Don't output the contents of <script> tags;
+  else if (mTagStackIndex > 0 &&
+           (mTagStack[mTagStackIndex-1] == eHTMLTag_script ||
+            mTagStack[mTagStackIndex-1] == eHTMLTag_style)) {
+    // Don't output the contents of <script> or <style> tags;
     return NS_OK;
   }
   else if (type == eHTMLTag_text) {
diff --git a/mozilla/content/base/test/Makefile.in b/mozilla/content/base/test/Makefile.in
index 44bc70f4032..d26858f3a41 100644
--- a/mozilla/content/base/test/Makefile.in
+++ b/mozilla/content/base/test/Makefile.in
@@ -111,6 +111,7 @@ _TEST_FILES = 	test_bug5141.html \
 		file_bug326337_multipart.txt^headers^ \
 		test_bug402150.html \
 		test_bug402150.html^headers^ \
+		test_bug401662.html \
 		$(NULL)
 
 libs:: $(_TEST_FILES)
diff --git a/mozilla/content/base/test/test_bug401662.html b/mozilla/content/base/test/test_bug401662.html
new file mode 100644
index 00000000000..314984bcf5c
--- /dev/null
+++ b/mozilla/content/base/test/test_bug401662.html
@@ -0,0 +1,50 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=401662
+-->
+<head>
+  <title>Test for Bug 401662</title>
+  <script type="text/javascript" src="/MochiKit/MochiKit.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=401662">Mozilla Bug 401662</a>
+<p id="display"></p>
+<div id="content" style="display: none">
+  <iframe id="testframe"
+          src="data:text/html,<html><body>foo<style>bar</style></body></html>">
+  </iframe>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+/** Test for Bug 401662 - don't serialize style elements in body into
+    plaintext**/
+SimpleTest.waitForExplicitFinish();
+
+window.onload = function() {
+  netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
+  const Cc = Components.classes;
+  const Ci = Components.interfaces;
+
+  var encoder = Cc["@mozilla.org/layout/documentEncoder;1?type=text/html"]
+                   .createInstance(Ci.nsIDocumentEncoder);
+
+  var doc = $("testframe").contentDocument;
+
+  encoder.init(doc, "text/plain", encoder.OutputBodyOnly);
+  encoder.setCharset("UTF-8");
+
+  var out = encoder.encodeToString();
+
+  is(out, "foo", "style content serialized in plaintext?");
+
+  SimpleTest.finish();
+}
+</script>
+</pre>
+</body>
+</html>
+
