grep "--color=always" doesn't work with "-i"

[Ottavio Caruso <ottavio2006-usenet2012%yahoo.com@localhost>]

Hi,

$ uname -a
NetBSD NetBSD 9.0_STABLE NetBSD 9.0_STABLE (GENERIC) #0: Sat May  9 
08:21:36 UTC 2020 
mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/amd64/compile/GENERIC amd64

My shell is ksh.


/usr/bin/grep --color=always "DUID" -r /usr/share/man/man*

correctly returns all manual page lines with "DUID" highlighted in red, 
where as:

/usr/bin/grep --color=always -i "DUID" -r /usr/share/man/man*

returns all manual page lines with case insensitive "duid" but without 
highlighting. I have tried to play around with the orders of parameters 
and removing quotes, without success.

As a term of comparison, the same command works as intended on OpenBSD 
and Linux.

Am I doing something wrong or is it a bug?


--
Ottavio Caruso