Issue #8072 has been updated by nagachika (Tomoyuki Chikanaga). Backport set to 1.9.3: DONTNEED, 2.0.0: REQUIRED ---------------------------------------- Bug #8072: Method#arity for keyword arguments https://bugs.ruby-lang.org/issues/8072#change-43897 Author: marcandre (Marc-Andre Lafortune) Status: Closed Priority: Normal Assignee: matz (Yukihiro Matsumoto) Category: core Target version: current: 2.1.0 ruby -v: r39608 Backport: 1.9.3: DONTNEED, 2.0.0: REQUIRED I would expect the following two methods to have the same arity: def old_way(req, options = {}); end def new_way(req, **options); end method(:new_way).arity # => 1, should be -2 -- http://bugs.ruby-lang.org/