Facility name disapears with merging

[FerreolS]

When I merge GW_Ori files (files from LITpro test folder in CVS), the facility name becomes undefined:

% oilist GW_Ori.200*
target_name	s_ra	s_dec	t_exptime	t_min	t_max	em_res_power	em_min	em_max	facility_name	instrument_name	nb_vis	nb_vis2	nb_t3	nb_channels	
GW_Ori	82.28334	11.87	0.0	52973.32806712948	52973.38412037026	6.6666665135530785	1.6499999446750735E-6	1.6499999446750735E-6	IOTA_AB	IONIC3	0	18	6	1	
GW_Ori	82.28334	11.87	0.0	52974.37421296304	52974.37674768502	6.6666665135530785	1.6499999446750735E-6	1.6499999446750735E-6	IOTA_AB	IONIC3	0	9	3	1	
GW_Ori	82.28334	11.87	0.0	53351.20174189797	53351.39668981498	6.6666665135530785	1.6499999446750735E-6	1.6499999446750735E-6	IOTA_AB	IONIC3	0	57	19	1	
GW_Ori	82.28334	11.87	0.0	53353.34997685207	53353.38156828703	6.6666665135530785	1.6499999446750735E-6	1.6499999446750735E-6	IOTA_AB	IONIC3	0	18	6	1	
GW_Ori	82.28334	11.87	0.0	53354.35648148134	53354.38167824084	6.6666665135530785	1.6499999446750735E-6	1.6499999446750735E-6	IOTA_AB	IONIC3	0	12	4	1	
GW_Ori	82.28334	11.87	0.0	53355.22764467588	53355.26708333334	6.6666665135530785	1.6499999446750735E-6	1.6499999446750735E-6	IOTA_AB	IONIC3	0	15	5	1	
GW_Ori	82.28334	11.87	0.0	53359.32408564817	53359.35291666677	6.6666665135530785	1.6499999446750735E-6	1.6499999446750735E-6	IOTA_AB	IONIC3	0	9	3	1	
% oimerge -o GW_Ori.2004Dec_merged.oifits GW_Ori.2004Dec.A28B*
Writing: GW_Ori.2004Dec_merged.oifits
% oilist GW_Ori.2004Dec_merged.oifits 
target_name	s_ra	s_dec	t_exptime	t_min	t_max	em_res_power	em_min	em_max	facility_name	instrument_name	nb_vis	nb_vis2	nb_t3	nb_channels	
GW_Ori	82.28334	11.87	0.0	53351.20174189797	53351.39668981498	6.6666665135530785	1.6499999446750735E-6	1.6499999446750735E-6	UNDEFINED	IONIC3	0	57	19	1	
GW_Ori	82.28334	11.87	0.0	53353.34997685207	53353.38156828703	6.6666665135530785	1.6499999446750735E-6	1.6499999446750735E-6	UNDEFINED	IONIC3	0	18	6	1	
GW_Ori	82.28334	11.87	0.0	53354.35648148134	53354.38167824084	6.6666665135530785	1.6499999446750735E-6	1.6499999446750735E-6	UNDEFINED	IONIC3	0	12	4	1	
GW_Ori	82.28334	11.87	0.0	53355.22764467588	53355.26708333334	6.6666665135530785	1.6499999446750735E-6	1.6499999446750735E-6	UNDEFINED	IONIC3	0	15	5	1	
GW_Ori	82.28334	11.87	0.0	53359.32408564817	53359.35291666677	6.6666665135530785	1.6499999446750735E-6	1.6499999446750735E-6	UNDEFINED	IONIC3	0	9	3	1