- return unless @buffers.length > 1
- @buffers.last.force_to_top = false
- raise_to_front @buffers[@buffers.length - 2]
+ bufs = rollable_buffers
+ return unless bufs.length > 1
+ bufs.last.force_to_top = false
+ raise_to_front bufs[bufs.length - 2]
+ end
+
+ def rollable_buffers
+ @buffers.select { |b| !b.system? || @buffers.last == b }