[luatex] using fea files in plain TeX

[Vafa Khalighi]

How do you usually use feature files in luatex. I have followed the
instruction at wiki. but it seems I can not use it in Plain TeX. I have
attached the files and the error I get is:

This is LuaTeX, Version beta-0.40.3-2009060821 (Web2C 2009)
(test.tex <luatex-fonts-merged.lua> <luatex-fonts.lua loaded in 0.020
seconds>
! LuaTeX error ...exmf/tex/luatex/luatex-fonts/luatex-fonts-merged.lua:1782:
ba
d argument #1 to 'lower' (string expected, got nil).
<to be read again>
                   \body
l.11 ...calt;featurefile=palatino.fea at 14pt\body

?
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