groovy2.5.6 final variable error

[joud . kassem79]

Hi all,

I upgraded to groovy 2.5.6 and am compiling my grails 4 project. I got this 
error:

The variable [version] is declared final but is reassigned

And the related code is something like this:

void upgrade() {
     final String version
     version = "something”
                  }

Anyone knows why am getting this error? The variable is assigned only once.

Thanks in advance