HTMLEncoder requiring StringBuilder class from JDK 5

I'm developing a JSF application using MyFaces 1.1.7 under JBoss 3.2.6 and JDK 1.4. Everything was OK (had deployed it several times) untill I added the following code to the page:

<h:outputLink value="secondPage.jsf" target="_blank">
<h:outputText value="Click here" />
<f:param name="myParam" value="#

" />
</h:outputLink>

This is resulting in the following exception:

java.lang.NoClassDefFoundError: java/lang/StringBuilder
at org.apache.myfaces.shared_impl.renderkit.html.util.HTMLEncoder.encodeURIAtributte(HTMLEncoder.java:355)
at org.apache.myfaces.shared_impl.renderkit.html.HtmlResponseWriterImpl.writeURIAttribute(HtmlResponseWriterImpl.java:393)
at org.apache.myfaces.shared_impl.renderkit.html.HtmlLinkRendererBase.renderOutputLinkStart(HtmlLinkRendererBase.java:461)
at org.apache.myfaces.shared_impl.renderkit.html.HtmlLinkRendererBase.encodeBegin(HtmlLinkRendererBase.java:93)

I downloaded the source code of HTMLEncoder.java from myfaces-impl-1.1.7.jar and confirmed that it's using a StringBuilder object within encodeURIAtributte method.

The question is: isn't myfaces 1.1.7 supposed to be compatible with JDK 1.4?

Thank in advance,
Rafael