wro4j-maven-plugin/src/main/java/ro/isdc/wro/maven/plugin/AbstractWro4jMojo.java
protected final void extendPluginClasspath()
      throws MojoExecutionException {
    // this code is inspired from http://teleal.org/weblog/Extending%20the%20Maven%20plugin%20classpath.html
    final List<String> classpathElements = new ArrayList<String>();
    try {
      classpathElements.addAll(mavenProject.getRuntimeClasspathElements());
    } catch (final DependencyResolutionRequiredException e) {
      throw new MojoExecutionException("Could not get compile classpath elements", e);
    }
    final ClassLoader classLoader = createClassLoader(classpathElements);
    Thread.currentThread().setContextClassLoader(classLoader);
  }
protected final void extendPluginClasspath()
      throws MojoExecutionException {
    // this code is inspired from http://teleal.org/weblog/Extending%20the%20Maven%20plugin%20classpath.html
    final List<String> classpathElements = new ArrayList<String>();
    try {
      classpathElements.addAll(mavenProject.getRuntimeClasspathElements());
    } catch (final DependencyResolutionRequiredException e) {
      throw new MojoExecutionException("Could not get compile classpath elements", e);
    }
    final ClassLoader classLoader = createClassLoader(classpathElements);
    Thread.currentThread().setContextClassLoader(classLoader);
  }
Update the classpath.