How to define key binding for Shift-TAB in .infokey?

[Clark Wang]

I'm using "info --vi-keys" and I have the following line in my .infokey:

    #info
    \e[z    move-to-prev-xref  # Shift-TAB

On macOS (info 4.8) it works fine but on my Linux (info 6.5) it reported
"Unknow command (BackTab)" when I press Shift-TAB. On both systems I'm
using TERM=linux and both's "infocmp" outputs "kcbt=\E[Z" .

Thanks.

-clark