BuildError couldn't understand kern.osversion `14.3.0'

[Steven Spiel]

I'm having trouble installing this gem on Yosemite 10.10.3.

Getting the error:

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

    /Users/stevenspiel/.rbenv/versions/2.1.2/bin/ruby -r ./siteconf20150615-63123-lm07gr.rb extconf.rb
extconf.rb:44:in `<main>': Use RbConfig instead of obsolete and deprecated Config.
extconf.rb:44:in `<main>': Use RbConfig instead of obsolete and deprecated Config.
create /Users/stevenspiel/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/rb-appscript-0.6.1/src/osx_ruby.h ...
create /Users/stevenspiel/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/rb-appscript-0.6.1/src/osx_intern.h ...
creating Makefile

make "DESTDIR=" clean

make "DESTDIR="
compiling src/rbae.c
couldn't understand kern.osversion `14.3.0'
In file included from /System/Library/Frameworks/CoreServices.framework/Headers/CoreServices.h:55,
                 from /System/Library/Frameworks/Carbon.framework/Headers/Carbon.h:20,
                 from src/rbae.c:13:
/System/Library/Frameworks/CoreServices.framework/Frameworks/FSEvents.framework/Headers/FSEvents.h:262: error: expected ‘,’ or ‘}’ before ‘__attribute__’
/System/Library/Frameworks/CoreServices.framework/Frameworks/FSEvents.framework/Headers/FSEvents.h:414: error: expected ‘,’ or ‘}’ before ‘__attribute__’
make: *** [rbae.o] Error 1

make failed, exit code 2

Any clue as to what might be causing this?