pterm scrollbar does not appear

If pterm is started with the -sb option, the documented behaviour is that a scroll bar will appear. However, on Ubuntu, no scroll bar is present.

 1) The release of Ubuntu you are using, via 'lsb_release -rd' or System -> About Ubuntu
$ lsb_release -rd
Description: Ubuntu 13.04
Release: 13.04

 2) The version of the package you are using, via 'apt-cache policy pkgname' or by checking in Software Center
$ apt-cache policy pterm
pterm:
  Instalita: 0.62-10ubuntu0.1
  Kandidato: 0.62-10ubuntu0.1
  Version table:
 *** 0.62-10ubuntu0.1 0
        500 http://gb.archive.ubuntu.com/ubuntu/ raring-updates/universe amd64 Packages
        500 http://gb.archive.ubuntu.com/ubuntu/ raring-security/universe amd64 Packages
        100 /var/lib/dpkg/status
     0.62-10 0
        500 http://gb.archive.ubuntu.com/ubuntu/ raring/universe amd64 Packages

 3) What you expected to happen
pterm window appears with scrollbar present

 4) What happened instead
pterm window appears with no scrollbar present

Using the pterm binary from Fedora also results in the same behaviour on ubuntu, while it works fine on Fedora. Perhaps pterm needs to be changed to exempt itself from the overlay-scrollbars behaviour?