The following simple program demonstrates the problem:
def test(foo: 10)
foo
end
test(foo: nil)
MRI:
2.0.0p247 :006 > test(foo: nil)
=> nil
JRuby:
jruby-1.7.4 :005 > test(foo: nil)
ArgumentError: unknown keyword: foo
from (irb):5:in `evaluate'
from org/jruby/RubyKernel.java:1093:in `eval'
from org/jruby/RubyKernel.java:1489:in `loop'
from org/jruby/RubyKernel.java:1254:in `catch'
from org/jruby/RubyKernel.java:1254:in `catch'
from /Users/jaz/.rvm/rubies/jruby-1.7.4/bin/irb:13:in `(root)'