Gr_dd_mpsk_sync_cc: error - "gr_complex must be 8-byte aligned"

Trying to experiment with the new MPSK block now in git. Getting the
following error message -

thread[thread-per-block[10]: <gr_block dd_mpsk_sync_cc (34)>]:
gr_complex must be 8-byte aligned

The ultimate source block in this case is a
gr.file_source(gr.sizeof_gr_complex,…)

The python program was working using the older gr_mpsk_receiver_cc.
This is what happened when attempting to substitute the newer
gr_dd_mpsk_sync…

Any ideas ?

Max