Issue #7897 has been reported by mrkn (Kenta Murata). ---------------------------------------- Bug #7897: rubygems 2.0 has an incompatibility about installation of extension libraries if gem package does not contain lib directory https://bugs.ruby-lang.org/issues/7897 Author: mrkn (Kenta Murata) Status: Open Priority: Urgent Assignee: drbrain (Eric Hodel) Category: lib Target version: 2.0.0 ruby -v: ruby 2.0.0dev (2013-02-08 trunk 39161) [x86_64-darwin11.4.2] Hi, rubygems 2.0 has an incompatibility about installation of extension libraries. If a gem package does not contain lib directory, an extension library file is copied as a file named "lib". You can reproduce this problem by installing msgpack version 0.4.7. -- http://bugs.ruby-lang.org/