Forum: Ruby on Rails rails 4.0.0.beta1 installation error

I am getting the following error while installing on windows with ruby v
2.0. I have installed DevKit for 64 bit.

Temporarily enhancing PATH to include DevKit...
Building native extensions.  This could take a while...
ERROR:  Error installing rails:
        ERROR: Failed to build gem native extension.

    d:/programs/Ruby200-x64/bin/ruby.exe extconf.rb
creating Makefile

make
generating atomic_reference-x64-mingw32.def
compiling atomic_reference.c
atomic_reference.c:1:0: error: CPU you selected does not support x86-64
instruct
ion set
make: *** [atomic_reference.o] Error 1


Gem files will remain installed in
d:/programs/Ruby200-x64/lib/ruby/gems/2.0.0/g
ems/atomic-1.0.1 for inspection.
Results logged to
d:/programs/Ruby200-x64/lib/ruby/gems/2.0.0/gems/atomic-1.0.1/
ext/gem_make.out

I get the same error, I solved with the 32bit version, ruby+devkit

Same error. Any ideas for workaround without switching to 32bit version 
or Ruby? My CPU is indeed a x86-64 compatible CPU.