Groovy stub generator generate invalid file for return value with generic type

Hi I migrated to 1.8.7 from 1.8.6 and now have problem with groovy stub generator, here is my class

 
class MessagingTask<T extends Serializable> {

  private static final long serialVersionUID = -5533069690405593263L;

  Long id
  String messageId
  String inDestination
  String outDestination
  MessagingTaskType messageType
  T messagePayload

  public String toString() {
    return "Task{" +
            "id=" + id +
            ", messageId='" + messageId + '\'' +
            ", inDestination='" + inDestination + '\'' +
            ", outDestination='" + outDestination + '\'' +
            ", messageType='" + messageType + '\'' +
            ", messagePayload=" + messagePayload +
            '}';
  }
}

and here is ant error:

groovy.compile:
[mkdir] Created dir: /home/sargis/projects/twm3.git/modules/accounting/Server/classes
[groovyc] Compiling 186 source files to /home/sargis/projects/twm3.git/modules/accounting/Server/classes
[groovyc] org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
[groovyc] Compile error during compilation with javac.
[groovyc] warning: [options] bootstrap class path not set in conjunction with -source 1.6
[groovyc] /tmp/groovy-generated-5697683262775722553-java-source/com/webbfontaine/twm/accounting/epaylog/emess/task/MessagingTask.java:28: error: incompatible types
[groovyc] public T getMessagePayload()

[groovyc] ^
[groovyc] required: T
[groovyc] found: Serializable
[groovyc] where T is a type-variable:
[groovyc] T extends Serializable declared in class MessagingTask
[groovyc] Note: /home/sargis/projects/twm3.git/modules/accounting/Server/src/com/webbfontaine/twm/accounting/epaylog/repository/request/RequestDatabase.java uses or overrides a deprecated API.
[groovyc] Note: Recompile with -Xlint:deprecation for details.
[groovyc] Note: Some input files use unchecked or unsafe operations.
[groovyc] Note: Recompile with -Xlint:unchecked for details.
[groovyc] 1 error
[groovyc] 1 warning
[groovyc]
[groovyc]
[groovyc] 1 error

BUILD FAILED

also want to mention that I was able to compile my project with IntelliJ groovy compiler. Thanks in advance.