Loading Sidekiq web: No 'transform_keys' method

After updating the gems listed above, an error is raised when attempting to load the Sidekiq website. The full error message can be seen here. The ruby version used is ruby 2.6.0p0 (2018-12-25 revision 66547) [x86_64-linux].

NoMethodError (undefined method `transform_keys' for <ActionDispatch::Request::Session:0x00005568df2a8710>):

The gems that were updated are:

selenium-webdriver 3.142.7
mime-types 3.3.1
mini_magick 4.10.1
image_processing 1.10.3
groupdate 4.3.0
friendly_id 5.3.0
faraday 0.17.3
http 4.3.0
public_suffix 4.0.3
rack 2.1.1
crass 1.0.6
i18n 1.7.1
minitest 5.14.0

The error is caused by the gem rack 2.1.1. Downgrade the rack gem to version to resolve the issue.