ruby 2.2 install error

[lilijreey]

ERROR: Error installing em-websocket: invalid gem: package is corrupt, exception while verifying: undefined method 'size' for nil:NilClass

[igrigorik]

Can't reproduce here

igrigorik { ~ } > ruby -v
ruby 2.2.4p230 (2015-12-16 revision 53155) [x86_64-darwin15]
igrigorik { ~ } > gem install em-websocket
Fetching: em-websocket-0.5.1.gem (100%)
Successfully installed em-websocket-0.5.1
1 gem installed

[lilijreey]

I reinstall with verion 5.0 is OK (git-master):~$ ruby -v ruby 2.1.4p265 (2014-10-27 revision 48166) [x86_64-linux] ruby version is 2.1.4 not 2.2 -_-!