Force an object to previous state, when using lock_version

If I have an exception while trying to save an object, how can I tell
Rails that it's not saved yet?

The object has a lock_version (used for optimistic locking). This is
what I do:

ins = MyClass.new( arguments )
begin
transaction do
  ins.save!
  bunch_of_other_stuff()
end
rescue
  ins.save! # problem here!
end

The object's save() sets the internal object state in a saved mode. It
actually isn't saved because the transaction failed.
I can't reload it, because it's not in the database yet, and all
subsequent saves are failing because the lock_version is wrong.

What I currently do, as a work-around is create a new instance of the
object:
new_ins = MyClass.new ( ins.attributes )

Is there any way I can tell Rails that this object was never saved
before?

Thanks,
Amir