Ase.contrain gives error indices has wrong amount of dimensions

Hi,
I am using ase to create selactive dynamics (FixedLine class). Below is my full code:

import os

import ase.io as aio
from ase.build import add_adsorbate, graphene, sort
from ase.calculators.vasp import Vasp
from ase.constraints import FixedLine

command = 'mpirun -np {:2d}  $HOME/bin/vasp_gam'.format(8)

os.environ['VASP_PP_PATH'] = os.path.expanduser('~/Software/POTCAR')

system = aio.read("Fe1.cif")
c = FixedLine(indices=[atom.index for atom in system], direction=[0, 0, 1])
system.set_constraint(c)
print(system)
calc = Vasp(directory="/tmp", command=command)
calc.set(ibrion=2,
         nsw=3,
         nelm=5,
         ediffg=-0.01,
         nelmdl=4,
         lreal="Auto",
         ncore=4,
         lorbit=11,
         lwave=False,
         lcharge=False)

system.calc = calc
print(system.get_potential_energy())

But this is giving error:

python trial.py 
Atoms(symbols='Fe4', pbc=True, cell=[3.65555117, 3.65555117, 3.65555117], spacegroup_kinds=..., constraint=FixedLine(indices=[0 1 2 3], [0.0, 0.0, 1.0]))
Traceback (most recent call last):
  File "/home/rudra/Projects/Porphyrine/trial.py", line 29, in <module>
    print(system.get_potential_energy())
          ~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/home/rudra/.local/lib/python3.13/site-packages/ase/atoms.py", line 770, in get_potential_energy
    energy = self._calc.get_potential_energy(self)
  File "/home/rudra/.local/lib/python3.13/site-packages/ase/calculators/abc.py", line 24, in get_potential_energy
    return self.get_property(name, atoms)
           ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/home/rudra/.local/lib/python3.13/site-packages/ase/calculators/calculator.py", line 538, in get_property
    self.calculate(atoms, [name], system_changes)
    ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/rudra/.local/lib/python3.13/site-packages/ase/calculators/vasp/vasp.py", line 346, in calculate
    self.read_results()
    ~~~~~~~~~~~~~~~~~^^
  File "/home/rudra/.local/lib/python3.13/site-packages/ase/calculators/vasp/vasp.py", line 564, in read_results
    calc_xml = self._read_xml()
  File "/home/rudra/.local/lib/python3.13/site-packages/ase/calculators/vasp/vasp.py", line 711, in _read_xml
    _xml_atoms = read(file, index=-1, format='vasp-xml')
  File "/home/rudra/.local/lib/python3.13/site-packages/ase/io/formats.py", line 809, in read
    return next(_iread(filename, slice(index, None), format, io,
                       parallel=parallel, **kwargs))
  File "/home/rudra/.local/lib/python3.13/site-packages/ase/parallel.py", line 302, in new_generator
    for result in generator(*args, **kwargs):
                  ~~~~~~~~~^^^^^^^^^^^^^^^^^
  File "/home/rudra/.local/lib/python3.13/site-packages/ase/io/formats.py", line 875, in _iread
    for dct in io.read(fd, *args, **kwargs):
               ~~~~~~~^^^^^^^^^^^^^^^^^^^^^
  File "/home/rudra/.local/lib/python3.13/site-packages/ase/io/vasp.py", line 485, in read_vasp_xml
    constraints.append(FixScaled(cell_init, i, flags))
                       ~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^
  File "/home/rudra/.local/lib/python3.13/site-packages/ase/constraints.py", line 887, in __init__
    super().__init__(indices=a)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^
  File "/home/rudra/.local/lib/python3.13/site-packages/ase/constraints.py", line 137, in __init__
    raise ValueError('indices has wrong amount of dimensions. '
                     f'Got {np.ndim(indices)}, expected ndim <= 1')
ValueError: indices has wrong amount of dimensions. Got 2, expected ndim <= 1

I am using ase-3.23.1b1 with Python 3.13.0

Any clue to solve this?