Can't run rspec when using Rails 5 and acts-as-taggable-on 4

Versions

• Ruby: 2.3.3
• Bundler: 1.14.6
• Rails: 5.0.2
• acts-as-taggable-on: 4.0.0

Gemfile

gem 'rails', '~> 5.0.0', '>= 5.0.0.1'
gem 'acts-as-taggable-on', '~> 4.0'

Exception

When running rpsec, got these errors:

/Users/user/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.14.6/lib/bundler/runtime.rb:94:in `rescue in block (2 levels) in require': There was an error while trying to load the gem 'acts-as-taggable-on'. (Bundler::GemRequireError)
Gem Load Error is: uninitialized constant ActsAsTaggableOn::GenericParser

How to fix it?