ClassCastException Double->Float with -= += operators and closures

 
void doesNotWork() {
  float myFloat = 40f
  myFloat -= 20f
  println "doesNotWork() $myFloat" // the exception is thrown here, but because of the combination of the -= and the closure
  (0..1).each { i -> // this can be any closure - doesn't matter
    println "doesNotWork() in the closure: $myFloat"
  }
}