Error in plot time domain data with filtfilt=True

I am trying to plot the observational data by plot_time_domain_data. However, an IndexError is obtained when I set filtfilt=True.

For example, I run the example, plot_time_domain_data.py https://git.ligo.org/lscsoft/bilby/blob/master/examples/gw_examples/injection_examples/plot_time_domain_data.py, then the following error appears.

File "plot_time_domain_data.py", line 38, in t0=t0) File "/usr/local/lib/python3.7/site-packages/bilby-0.5.9-py3.7.egg/bilby/gw/detector/interferometer.py", line 673, in plot_time_domain_data strain = timeseries.filter(zpk, filtfilt=True) File "/usr/local/lib/python3.7/site-packages/gwpy/timeseries/timeseries.py", line 1118, in filter out = signal.sosfiltfilt(sos, self, **kwargs) File "/usr/local/lib/python3.7/site-packages/scipy/signal/signaltools.py", line 3402, in sosfiltfilt ntaps=ntaps) File "/usr/local/lib/python3.7/site-packages/scipy/signal/signaltools.py", line 3204, in _validate_pad ext = odd_ext(x, edge, axis=axis) File "/usr/local/lib/python3.7/site-packages/scipy/signal/arraytools.py", line 98, in odd_ext left_end = axis_slice(x, start=0, stop=1, axis=axis) File "/usr/local/lib/python3.7/site-packages/scipy/signal/arraytools.py", line 45, in axis_slice b = a[tuple(a_slice)] File "/usr/local/lib/python3.7/site-packages/gwpy/types/series.py", line 596, in getitem sliceutils.slice_axis_attributes(self, 'x', new, 'x', slice) File "/usr/local/lib/python3.7/site-packages/gwpy/types/sliceutils.py", line 75, in slice_axis_attributes setattr(new, index(newaxis), getattr(old, index(oldaxis))[slice]) File "/usr/local/lib/python3.7/site-packages/gwpy/types/series.py", line 319, in xindex self._set_index("xindex", index) File "/usr/local/lib/python3.7/site-packages/gwpy/types/series.py", line 225, in _set_index setattr(self, delta, index[1] - index[0]) File "/usr/local/lib/python3.7/site-packages/gwpy/types/index.py", line 89, in getitem item = super(Index, self).getitem(key) File "/usr/local/lib/python3.7/site-packages/astropy/units/quantity.py", line 1038, in getitem out = super().getitem(key) IndexError: index 1 is out of bounds for axis 0 with size 1

If I set filtfilt=False, the error does not appear and I can obtain the time domain plot. Thus, I think it may be a kind of bugs regarding filter settings. I am using bilby 0.5.9 and python 3.7.