AssertionError in `_check_cluster_list_consistency`

Traceback:

Traceback (most recent call last):
  File "/home/martin/src/mair/scripts/cluster_fail_mwe.py", line 9, in <module>
    supercell_factor=4
  File "/home/martin/src/clease/clease/settings_bulk.py", line 92, in __init__
    ignore_background_atoms)
  File "/home/martin/src/clease/clease/settings.py", line 97, in __init__
    self._check_cluster_list_consistency()
  File "/home/martin/src/clease/clease/settings.py", line 627, in _check_cluster_list_consistency
    cluster_list.sort()
  File "/home/martin/src/clease/clease/cluster_list.py", line 106, in sort
    self.clusters.sort()
  File "/home/martin/src/clease/clease/cluster.py", line 26, in __lt__
    assert self.name >= other.name
AssertionError

with the following MWE:

import clease

bulk = clease.CEBulk(
    crystalstructure='fcc',
    a=2.8,
    concentration=clease.Concentration([['Mg', 'Zn', 'Ca']]),
    supercell_factor=4
)

Same result if supercell_factor is not present - just takes longer.