Runtime dependency on activerecord (~> 5.0) prevents upgrade to Rails 5.1

[keithpitty]

I'm gradually upgrading a Rails application that uses acts-as-taggable-on. When attempting to bundle update having set Rails to the latest version in the 5.1 path, bundler reports an incompatibility:

Bundler could not find compatible versions for gem "activerecord":
  In Gemfile:
    acts-as-taggable-on (~> 6.0.0) was resolved to 6.0.0, which depends on
      activerecord (~> 5.0)

    rails (~> 5.1.6.1) was resolved to 5.1.6.1, which depends on
      activerecord (= 5.1.6.1)

I see from https://rubygems.org/gems/acts-as-taggable-on/versions/6.0.0 that there is a runtime dependency on activerecord (~> 5.0). Why does this dependency exist? Should acts-as-taggable-on support Rails 5.1 and 5.2?

[x1wins]

I used gem 'rails', '~> 6.0.0.rc1' and I have same problem

Resolving dependencies...
Bundler could not find compatible versions for gem "activerecord":
  In Gemfile:
    acts-as-taggable-on (~> 6.0) was resolved to 6.0.0, which depends on
      activerecord (~> 5.0)

    rails (~> 6.0.0.rc1) was resolved to 6.0.0.rc1, which depends on
      activerecord (= 6.0.0.rc1)