diff --git a/content/base/src/nsPlainTextSerializer.cpp b/content/base/src/nsPlainTextSerializer.cpp
index 7c0b0bca6b62..98dfc7aeab34 100644
--- a/content/base/src/nsPlainTextSerializer.cpp
+++ b/content/base/src/nsPlainTextSerializer.cpp
@@ -140,6 +140,7 @@ nsPlainTextSerializer::~nsPlainTextSerializer()
 {
   delete[] mTagStack;
   delete[] mOLStack;
+  NS_WARN_IF_FALSE(mHeadLevel == 0, "Wrong head level!");
 }
 
 NS_IMPL_ISUPPORTS4(nsPlainTextSerializer, 
@@ -439,6 +440,7 @@ nsPlainTextSerializer::AppendElementEnd(nsIDOMElement *aElement,
 
   if (id == eHTMLTag_head) {
     --mHeadLevel;
+    NS_ASSERTION(mHeadLevel >= 0, "mHeadLevel < 0");
   }
 
   return rv;
@@ -478,6 +480,7 @@ nsPlainTextSerializer::CloseContainer(const nsHTMLTag aTag)
 {
   if (aTag == eHTMLTag_head) {
     --mHeadLevel;
+    NS_ASSERTION(mHeadLevel >= 0, "mHeadLevel < 0");
     return NS_OK;
   }
 
@@ -514,6 +517,7 @@ nsPlainTextSerializer::AddLeaf(const nsIParserNode& aNode)
 NS_IMETHODIMP 
 nsPlainTextSerializer::OpenHead()
 {
+  ++mHeadLevel;
   return NS_OK;
 }
 
diff --git a/content/base/test/Makefile.in b/content/base/test/Makefile.in
index 2d0a02d3e832..8b8491a7fc2c 100644
--- a/content/base/test/Makefile.in
+++ b/content/base/test/Makefile.in
@@ -43,7 +43,7 @@ relativesrcdir  = content/base/test
 
 include $(DEPTH)/config/autoconf.mk
 
-CPP_UNIT_TESTS += TestNativeXMLHttpRequest.cpp
+CPP_UNIT_TESTS += TestNativeXMLHttpRequest.cpp TestPlainTextSerializer.cpp
 
 LOCAL_INCLUDES += -I$(topsrcdir)/xpcom/tests
 
@@ -56,6 +56,7 @@ REQUIRES += \
   string \
   xpcom \
   xpconnect \
+  htmlparser \
   $(NULL)
 
 CPPSRCS += $(CPP_UNIT_TESTS)
diff --git a/content/base/test/TestPlainTextSerializer.cpp b/content/base/test/TestPlainTextSerializer.cpp
new file mode 100644
index 000000000000..065cfc98fda2
--- /dev/null
+++ b/content/base/test/TestPlainTextSerializer.cpp
@@ -0,0 +1,108 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* ***** BEGIN LICENSE BLOCK *****
+ * Version: MPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Mozilla Public License Version
+ * 1.1 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+ * for the specific language governing rights and limitations under the
+ * License.
+ *
+ * The Original Code is mozilla.org code.
+ *
+ * The Initial Developer of the Original Code is Mozilla Foundation.
+ * Portions created by the Initial Developer are Copyright (C) 2008
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *   Olli Pettay <Olli.Pettay@helsinki.fi> (Original Author)
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either of the GNU General Public License Version 2 or later (the "GPL"),
+ * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the MPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the MPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+#include "TestHarness.h"
+
+#include "nsIParser.h"
+#include "nsIHTMLToTextSink.h"
+#include "nsIParser.h"
+#include "nsIContentSink.h"
+#include "nsIParserService.h"
+#include "nsServiceManagerUtils.h"
+#include "nsStringGlue.h"
+#include "nsParserCIID.h"
+
+#define REPORT_ERROR(_msg)                  \
+  printf("FAIL " _msg "\n")
+
+#define TEST_FAIL(_msg)                     \
+  PR_BEGIN_MACRO                            \
+    REPORT_ERROR(_msg);                     \
+    return NS_ERROR_FAILURE;                \
+  PR_END_MACRO
+
+static NS_DEFINE_CID(kCParserCID, NS_PARSER_CID);
+
+void
+ConvertBufToPlainText(nsString &aConBuf)
+{
+  nsCOMPtr<nsIParser> parser = do_CreateInstance(kCParserCID);
+  if (parser) {
+    nsCOMPtr<nsIContentSink> sink;
+    sink = do_CreateInstance(NS_PLAINTEXTSINK_CONTRACTID);
+    if (sink) {
+      nsCOMPtr<nsIHTMLToTextSink> textSink(do_QueryInterface(sink));
+      if (textSink) {
+        nsAutoString convertedText;
+        textSink->Initialize(&convertedText, 0, 72);
+        parser->SetContentSink(sink);
+        parser->Parse(aConBuf, 0, NS_LITERAL_CSTRING("text/html"), PR_TRUE);
+        aConBuf = convertedText;
+      }
+    }
+  }
+}
+
+nsresult
+TestPlainTextSerializer()
+{
+  nsString test;
+  test.AppendLiteral("<html><base>base</base><head><span>span</span></head>"
+                     "<body>body</body></html>");
+  ConvertBufToPlainText(test);
+  if (!test.EqualsLiteral("basespanbody")) {
+    TEST_FAIL("Wrong html to text serialization");
+  }
+  printf("HTML to text serialization test PASSED!\n");
+
+  // Add new tests here...
+  return NS_OK;
+}
+
+int main(int argc, char** argv)
+{
+  ScopedXPCOM xpcom("PlainTextSerializer");
+  if (xpcom.failed())
+    return 1;
+
+  int retval = 0;
+  if (NS_FAILED(TestPlainTextSerializer())) {
+    retval = 1;
+  }
+
+  return retval;
+}