Requiring 'rbconfig' doesn't seem to create a constant CONFIG (Windows)

gistfile1.txt

C:\>irb
irb(main):001:0> CONFIG
NameError: uninitialized constant Object::CONFIG
        from (irb):1
        from C:/Ruby192/bin/irb:12:in `<main>'
irb(main):002:0> require 'rbconfig'
=> true
irb(main):003:0> CONFIG
NameError: uninitialized constant Object::CONFIG
        from (irb):3
        from C:/Ruby192/bin/irb:12:in `<main>'

# It doesn't seem to be the "require 'rbconfig'" that creates the CONFIG constant