Jenkins Gradle Plugin - 2nd invoke call to "Invoke Gradle Script" within a Jenkins job, makes first call lose Gradle version list/box

Inside a job. Under Build section, invoke Gradle Script section twice.

call "clean build" in first call
call "clean build someothertarget" or "someothertargetonly"

save the config/job.
open it again, you'll find that first Invoke gradle call has lost "Gradle Version" list/box value. I'm using gradle defined in Jenkins global settings as Gradle_1_6 instead of list/box value for Gradle Version as (default).