diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 165095c1e..14ca00bfe 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -11,7 +11,7 @@ permissions:
 
 jobs:
   rack-protection:
-    name: rack-protection (${{ matrix.ruby }}, Rack ${{ matrix.rack }})
+    name: rack-protection (${{ matrix.ruby }}, rack ${{ matrix.rack }}, rack-session ${{ matrix.rack_session }})
     runs-on: ubuntu-latest
     timeout-minutes: 5
     strategy:
@@ -19,6 +19,8 @@ jobs:
       matrix:
         rack:
           - stable
+        rack_session:
+          - stable
         ruby:
           - "2.6"
           - "2.7"
@@ -29,6 +31,10 @@ jobs:
           - "jruby"
           - "truffleruby"
           - "ruby-head"
+        include:
+          # Rack
+          - { ruby: 3.2, rack: head,   rack_session: stable }
+          - { ruby: 3.2, rack: stable, rack_session: head }
     env:
       rack: ${{ matrix.rack }}
     steps:
@@ -57,7 +63,7 @@ jobs:
       with:
         github-token: ${{ secrets.GITHUB_TOKEN }}
         webhook: ${{ secrets.DISCORD_WEBHOOK }}
-  test:
+  sinatra:
     name: ${{ matrix.ruby }} (Rack ${{ matrix.rack }}, Puma ${{ matrix.puma }}, Tilt ${{ matrix.tilt }})
     runs-on: ubuntu-latest
     timeout-minutes: 15
@@ -71,7 +77,7 @@ jobs:
         tilt:
           - stable
         # Due to https://github.com/actions/runner/issues/849, we have to use quotes for '3.0'
-        ruby: [2.6, 2.7, '3.0', 3.1, 3.2, 3.3, truffleruby]
+        ruby: [2.6, 2.7, '3.0', 3.1, 3.2, 3.3, jruby, truffleruby]
         include:
           # Rack
           - { ruby: 3.2, rack: head,   puma: stable,   tilt: stable, allow-failure: true }
@@ -79,10 +85,6 @@ jobs:
           - { ruby: 3.2, rack: stable, puma: head,     tilt: stable, allow-failure: true }
           # Tilt
           - { ruby: 3.2, rack: stable, puma: stable,   tilt: head, allow-failure: true }
-          # Due to flaky tests, see https://github.com/sinatra/sinatra/pull/1870
-          - { ruby: jruby-9.3, rack: stable, puma: stable, tilt: stable, allow-failure: true }
-          # Due to https://github.com/jruby/jruby/issues/7647
-          - { ruby: jruby-9.4, rack: stable, puma: stable, tilt: stable, allow-failure: true }
           # Never fail our build due to problems with head
           - { ruby: ruby-head,        rack: stable, puma: stable, tilt: stable, allow-failure: true }
           - { ruby: jruby-head,       rack: stable, puma: stable, tilt: stable, allow-failure: true }
diff --git a/Gemfile b/Gemfile
index 9b24134a2..6d56a2c8b 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,13 +1,5 @@
 # frozen_string_literal: true
 
-# Why use bundler?
-# Well, not all development dependencies install on all rubies. Moreover, `gem
-# install sinatra --development` doesn't work, as it will also try to install
-# development dependencies of our dependencies, and those are not conflict free.
-# So, here we are, `bundle install`.
-#
-# If you have issues with a gem: `bundle install --without-coffee-script`.
-
 source 'https://rubygems.org'
 gemspec
 
diff --git a/rack-protection/Gemfile b/rack-protection/Gemfile
index 44bba020f..c5f4b42f8 100644
--- a/rack-protection/Gemfile
+++ b/rack-protection/Gemfile
@@ -1,16 +1,18 @@
 # frozen_string_literal: true
 
 source 'https://rubygems.org'
-# encoding: utf-8
+gemspec
 
 gem 'rake'
 gem 'rspec', '~> 3'
+gem 'rack-test'
 
 rack_version = ENV['rack'].to_s
 rack_version = nil if rack_version.empty? || (rack_version == 'stable')
 rack_version = { github: 'rack/rack' } if rack_version == 'head'
 gem 'rack', rack_version
 
-gemspec
-
-gem 'rack-test'
+rack_session_version = ENV['rack_session'].to_s
+rack_session_version = nil if rack_session_version.empty? || (rack_session_version == 'stable')
+rack_session_version = { github: 'rack/rack-session' } if rack_session_version == 'head'
+gem 'rack-session', rack_session_version