'svn add' does not add 'svn:keywords', but 'svn ci' ask for it

1) svn add some_file
2) svn ci some_file
svn: Commit blocked by pre-commit hook (exit code 1) with output:
Path ".../some_file" is missing the 
svn:keywords property (or an fbsd:nokeywords override)

I manage it adding by hand:
3) svn propset svn:keywords 'FreeBSD:%H' some_file

It isn't convenient. Why 'svn add' can't do it automatically for 
me using the same detection method as 'svn ci'? 
P.S. I use subversion-freebsd-1.6.5 port.

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