Well given that all older OS X versions ship only with Ruby.framework 1.8 but 10.9 ships with 1.8 and 2.0 it is specific to Mavericks, but it doesn't break on older versions of OS X. Alternatively we could keep the code as is and compile against 2.0 framework event if the ruby-command passed is ruby 1.8 as in the case of homebrew. Alternatively I could look into the differences between the vim and macvim configure script, because the vim one already works fine with different framework rubies without patching.