Manifest file attribute overwrite

I have a manifest that I am using from a file. But I need to overwrite one attribute in that. I am using the following script but it doesn’t overwrite the value. What am I doing wrong:

jar {
  includeEmptyDirs = false
  manifest {
    from 'META-INF/MANIFEST.MF'
  }
  doLast {
  manifest {  
    attributes('Bundle-Classpath': 'test') //This is the value I want to overwrite
  }
}