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!