ant taskdef class cannot be found using the classloader

Po wpisaniu komenty ant build pojawa mi sietaki błąd: taskdef class pl.put.Metalink cannot be foundusing the classloader
tak wyglada build.xml

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<project basedir="." default="metalink-example" name="Metalink exercise">
    <property file="local.properties"/>
    <property file="default.properties"/>
    <path id="build.path">
        <pathelement location="target"/>
        <fileset dir="target/lib">
            <include name="**/*.jar"/>
        </fileset>
    </path>

    <taskdef name="metalink" classname="pl.put.Metalink" classpath="target/classes" classpathref="build.path"/>

    <target name="metalink-example">
        <metalink url="http://zad-zwiwo.com/download/" file="zad-zwiwo.xml">
            <fileset dir="." />
        </metalink>
    </target>
</project>