How to `bundle install` when your Gemfile requires an older version of bundler?

First you need to install the appropriate version of bundler:

% gem install bundler -v '~> 1.0.0'
Successfully installed bundler-1.0.22

Then force rubygems to use the version you want (see this post):

% bundle _1.0.22_ install

I had the same issue on macOS Mojave. I installed the different version of the bundler gem and uninstall the current version.

gem install bundler -i '2.0.1'

gem uninstall bundler

Then gives me the option to choose the version to uninstall and I choose the one which is creating the problem.

The error message In Gemfile: bundler (~> 1.16) is a bit inaccurate, since the version number requirement can come from other places, such as the .gemspec file, which was the case for me:

spec.add_development_dependency "bundler", "~> 1.16"

Removing the version number from the .gemspec file solved the issue for me:

spec.add_development_dependency "bundler"

This is what I had to do to get it to work to install with a previous version (2.2.11) of bundler:

gem install bundler:2.2.11
bundle _2.2.11_ install