Parasite overrides black arrow, is there any way to fix this

Level 4
Jan 23, 2017
I am trying to make a map where one unit type has a black arrow ability while another type has parasite, while 2 different parasite abilities do not override each other when different buffs are used, black arrow is override if it is used on unit before parasite, but both work if black arrow is used on unit after parasite. I'd love to know why this functions that way and also if there is a way to make parasite not override black arrow

both buffs always appear, but if parasite is used after black arrow the black arrow unit wont spawn