How to update pkg_install package?

[MATSUMURA Hidetoshi <bnj_2_h%muf.biglobe.ne.jp@localhost>]

Hi,
I updated NetBSD/i386 From 4.0.2 to 5.1, and updated pkgsrc to 2011Q2 
branch.
When I executed 'lintpkgsrc -i',results was "Version mismatch: 'pkg_i 
nstall' 20100915 vs 20110215".

Then I tried...
# cd /pkgsrc/pkgtools/pkg_install
# make update

But Results was here
...
===> Install binary package of pkg_install-20110215
pkg_add: A different version of pkg_install-20110215 is already insta 
lled: pkg_install-20100915
pkg_add: 1 package addition failed
*** Error code 1

Stop.
make: stopped in /pkgsrc/pkgtools/pkg_install
*** Error code 1

Stop.
make: stopped in /pkgsrc/pkgtools/pkg_install
*** Error code 1

Stop.
make: stopped in /pkgsrc/pkgtools/pkg_install

--------------------------------------------------------------------

Does anyone know how to update pkg_install package?

--
松村英俊(MATSUMURA Hidetoshi)
bnj_2_h%muf.biglobe.ne.jp@localhost , icarrot%mac.com@localhost