Issue #8261 has been reported by manveru (Michael Fellinger). ---------------------------------------- Bug #8261: module_function for methods of same name https://bugs.ruby-lang.org/issues/8261 Author: manveru (Michael Fellinger) Status: Open Priority: Low Assignee: Category: core Target version: current: 2.1.0 ruby -v: ruby 2.0.0p0 (2013-02-24 revision 39474) [x86_64-linux] This affects all versions from 1.8 to 2.0 I have tested. I'd expect all three examples below to have the same output, but not only does the example with module_function end up with a private instance method, it also has the wrong one. If the name of the method is different, it behaves as one would expect, this only happens if the methods have the same name. module A def a 1 end module_function def a 2 end end class X include A end module B def b 1 end def self.b 2 end end class Y include B end module C def c 1 end class << self def c 2 end end end class Z include C end p [A.a, X.new.send(:a)] # => [2, 2] p [B.b, Y.new.b] # => [2, 1] p [C.c, Z.new.c] # => [2, 1] -- http://bugs.ruby-lang.org/