Hi I am trying to run the following command phenix.twin_map_utils data.file=cy_p10_2_28.1_unique1.mtz model.file=cy_p10_2_28.1.pdb obs_labels=F_p10-2,SIGF_p10-2 free_flag=FreeR_flag When I run phenix.twin_map_utils from phenix version 1.3 final or from the newest cci_aps. I get the following AssertionError ( see below). I think my mtz file is kosher because phenix.refine with the twin_law option handles it well and I can refine with a twin law. Is there something wrong in the syntax or the file. I am attaching the log file with the Assertion Error to this email. Thanks for your help Hari Overall and bulk solvent scale paranmeters and twin fraction estimation ======================================================================= Traceback (most recent call last): File "/Users/hari/cci_apps_sources/mmtbx/mmtbx/command_line/twin_map_utils.py", line 7, in <module> twin_map_utils.run(args=sys.argv[1:]) File "/Users/hari/cci_apps_sources/mmtbx/mmtbx/twinning/twin_map_utils.py", line 306, in run out=log) File "/Users/hari/cci_apps_sources/mmtbx/mmtbx/twinning/twin_f_model.py", line 946, in __init__ assert self.f_obs.indices().all_eq( self.free_array.indices() ) AssertionError