Issue with mcmc_equilibrate in 2.27 (Ubuntu 16)

In version 2.27 I am unable to run mcmc_equilibrate. I get the following error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.6/site-packages/graph_tool/inference/mcmc.py", line 130, in mcmc_equilibrate
    delta, nattempts, nmoves = state.mcmc_sweep(**mcmc_args)
  File "/usr/lib/python3.6/site-packages/graph_tool/inference/nested_blockmodel.py", line 826, in mcmc_sweep
    c=c, **kwargs)
  File "/usr/lib/python3.6/site-packages/graph_tool/inference/nested_blockmodel.py", line 762, in _h_sweep
    for l, lstate, args in self._h_sweep_gen(**kwargs):
  File "/usr/lib/python3.6/site-packages/graph_tool/inference/nested_blockmodel.py", line 742, in _h_sweep_gen
    filt[0].a = not filt[1]
AttributeError: 'NoneType' object has no attribute 'a'

I get the same error from apt-get installation with python2 and python3 on Ubuntu 16 and Debian. I tried running it with the Docker image as well and got the same error. I can send a reproducible example but it is too large to upload here. The issue does not occur with graph-tool version 2.26. Is there anyway of installing older versions of graph-tool via apt-get?