gem install psych error

I'm trying to bundle install a rails project but I'm stuck... when I try to run gem install psych all I get is this:

Building native extensions.  This could take a while...
ERROR:  Error installing psych:
        ERROR: Failed to build gem native extension.

        /Users/gibatronic/.rvm/rubies/ruby-1.9.3-p327/bin/ruby extconf.rb
checking for yaml.h... no
yaml.h is missing. Try 'port install libyaml +universal' or 'yum install libyaml-devel'
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers.  Check the mkmf.log file for more
details.  You may need configuration options.

Provided configuration options:
    --with-opt-dir
    --without-opt-dir
    --with-opt-include
    --without-opt-include=${opt-dir}/include
    --with-opt-lib
    --without-opt-lib=${opt-dir}/lib
    --with-make-prog
    --without-make-prog
    --srcdir=.
    --curdir
    --ruby=/Users/gibatronic/.rvm/rubies/ruby-1.9.3-p327/bin/ruby
    --with-libyaml-dir
    --without-libyaml-dir
    --with-libyaml-include
    --without-libyaml-include=${libyaml-dir}/include
    --with-libyaml-lib
    --without-libyaml-lib=${libyaml-dir}/lib


Gem files will remain installed in /Users/gibatronic/.rvm/gems/ruby-1.9.3-p327/gems/psych-1.3.4 for inspection.
Results logged to /Users/gibatronic/.rvm/gems/ruby-1.9.3-p327/gems/psych-1.3.4/ext/psych/gem_make.out

I'm running ruby 1.9.3p327 with rails 3.2.12 on OS X 10.8.2

I've already installed libyaml 0.1.4 with rvm pkg install libyaml

I really don't know what to do anymore!

install libyaml

port install libyaml +universal