You can check your current version of bundler like so:
$ bundle --version 1.17.3
If you have older versions of bundler, you run against those by specifying the version in the command:
$ bundle _1.16.6_ --version 1.16.6
Likewise this can be used with any bundler command:
$ bundle _1.16.6_ install
sourcearrow-up-right
Last updated 4 years ago