Gem "Malformed Version Number String"

I'm building a gem. I just got the basic project structure laid out, and I tried building it with gem build my_gem.gemspec, which worked fine. Then I installed it with gem install My\ Gem-0.0.1.gem and it still looked like it worked fine. Then I tried to run irb and I got this:

/Users/<username>/.rbenv/versions/2.2.2/lib/ruby/2.2.0/rubygems/version.rb:206:in `initialize': Malformed version number string on (ArgumentError)

Then I tried making some changes and saved them. I ran gem build my_gem.gemspec. Same error. All irb, rails, and gem sub-commands are generating a stack trace with this at the top. What did I do to break all of these commands and how do I reverse it?

via Chebli Mohamed