Serializable class in groovy script

serialize.groovy

// The code below produces ClassNotFoundError. How to fix it?

import groovy.transform.ToString

@ToString
class P2ModuleSource implements Serializable {
  private static final long serialVersionUID = 3526473395612776159L
  List uris
  P2ModuleSource(List uris) {
    this.uris = uris
  }
}

def x = new P2ModuleSource(['aaa', 'bbb'])

def outBytes = new ByteArrayOutputStream()
def outs = new ObjectOutputStream(outBytes)
outs.writeObject(x)
outs.close()
def bytes = outBytes.toByteArray()

def inBytes = new ByteArrayInputStream(bytes)
def ins = new ObjectInputStream(inBytes)
def y = ins.readObject()