Installer crashes when specifiying partitions manuall and asking partition to be formatted

[Untitled No. 4]

Binary package hint: ubiquity

When installing Lucid (Kubuntu) and preparing disk space:
1. Choose "Specify partitions manually".
2. Highlight an existing partition and click Change.
3. Set to use as Ext4 and mount point / and tick Format the partition
4. Press OK and the installer closes with the following error:

Traceback (most recent call last):
  File "/usr/lib/ubiquity/ubiquity/frontend/kde_ui.py", line 1888, in on_partition_list_edit_activate
    self.partman_edit_dialog(devpart, partition)
  File "/usr/lib/ubiquity/ubiquity/frontend/kde_ui.py", line 1760, in partman_edit_dialog
    self.dbfilter.edit_partition(devpart, **edits)
TypeError: edit_partition() got an unexpected keyword argument 'format'

If you don't tick Format the partitio, click OK and then tick for the partition to be formatted everything works well.