Piping man into grep - grotty sgr0 message

[Michael J. Donovan]

Updated to 1.23.0
man works as before, except when you pipe its output to another command.
    man ls | grep color
    grotty:<standard input>:(<standard input>):9: warning: unrecognized 
X command 'sgr 0' ignored
       --color[=WHEN]

The same thing happens here:
    man ls | cat

In my .bashrc:
    export MANROFFOPT='-c'
    export GROFF_NO_SGR=1

The only way to suppress the grotty message is with brute force:
    man ls 2>/dev/null | grep color

-Mike