no such file to load -- iconv

trying to update an application (2.3.2 to 2.3.4) I run
rake rails:update --trace

got the error :
rake aborted!
no such file to load -- iconv
/usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in
`gem_original_require'

is it a missing lib in Ruby ?
I recently installed it from scratch
ruby 1.8.7 (2009-06-12 patchlevel 174) [i686-darwin10.0.0]

should I recompile it ?

try to recompile it with the option '--with-iconv-dir=/usr/
local' (replace /usr/local with whereever your iconv is installed).
That worked for me.

Andi