diff --git a/.github/workflows/ruby.yml b/.github/workflows/ruby.yml
index e7bc6554..0a1b1a25 100644
--- a/.github/workflows/ruby.yml
+++ b/.github/workflows/ruby.yml
@@ -32,7 +32,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby-version: [ '3.4', '3.3', '3.2', 'ruby-head' ]
+        ruby-version: [ '4.0', '3.4', '3.3', '3.2', 'ruby-head' ]
         gemfile: [ '8.1', '8.0', '7.2', 'edge' ]
         exclude:
           - ruby-version: 3.2
diff --git a/gemfiles/8.0.gemfile b/gemfiles/8.0.gemfile
index 32cf900d..adbc130f 100644
--- a/gemfiles/8.0.gemfile
+++ b/gemfiles/8.0.gemfile
@@ -8,3 +8,4 @@ gem "mutex_m" if Gem::Version.new(RUBY_VERSION) >= Gem::Version.new("3.4.0")
 gem "propshaft"
 gem "rails", "~> 8.0.1"
 gem "sqlite3"
+gem "json", "~> 2.21"
diff --git a/lib/bootstrap_form.rb b/lib/bootstrap_form.rb
index 5109147c..f98b1b7d 100644
--- a/lib/bootstrap_form.rb
+++ b/lib/bootstrap_form.rb
@@ -32,11 +32,10 @@ def deprecator
   end
 
   mattr_accessor :field_error_proc
-  # rubocop:disable Style/ClassVars
+  # rubocop:disable-next Style/ClassVars
   @@field_error_proc = proc do |html_tag, _instance_tag|
     html_tag
   end
-  # rubocop:enable Style/ClassVars
 end
 
 require "bootstrap_form/engine" if defined?(Rails)
diff --git a/lib/bootstrap_form/inputs/collection_select.rb b/lib/bootstrap_form/inputs/collection_select.rb
index c43091eb..38ad4bc1 100644
--- a/lib/bootstrap_form/inputs/collection_select.rb
+++ b/lib/bootstrap_form/inputs/collection_select.rb
@@ -8,7 +8,7 @@ module CollectionSelect
 
       included do
         # Disabling Metrics/ParameterLists because the upstream Rails method has the same parameters
-        # rubocop:disable Metrics/ParameterLists
+        # rubocop:disable-next Metrics/ParameterLists
         def collection_select_with_bootstrap(method, collection, value_method, text_method, options={}, html_options={})
           html_options = html_options.reverse_merge(control_class: "form-select")
           form_group_builder(method, options, html_options) do
@@ -17,7 +17,6 @@ def collection_select_with_bootstrap(method, collection, value_method, text_meth
             end
           end
         end
-        # rubocop:enable Metrics/ParameterLists
 
         bootstrap_alias :collection_select
       end
diff --git a/lib/bootstrap_form/inputs/grouped_collection_select.rb b/lib/bootstrap_form/inputs/grouped_collection_select.rb
index ab80d841..e0ba9948 100644
--- a/lib/bootstrap_form/inputs/grouped_collection_select.rb
+++ b/lib/bootstrap_form/inputs/grouped_collection_select.rb
@@ -8,7 +8,7 @@ module GroupedCollectionSelect
 
       included do
         # Disabling Metrics/ParameterLists because the upstream Rails method has the same parameters
-        # rubocop:disable Metrics/ParameterLists
+        # rubocop:disable-next Metrics/ParameterLists
         def grouped_collection_select_with_bootstrap(method, collection, group_method,
                                                      group_label_method, option_key_method,
                                                      option_value_method, options={}, html_options={})
@@ -21,7 +21,6 @@ def grouped_collection_select_with_bootstrap(method, collection, group_method,
             end
           end
         end
-        # rubocop:enable Metrics/ParameterLists
 
         bootstrap_alias :grouped_collection_select
       end
diff --git a/lib/bootstrap_form/inputs/inputs_collection.rb b/lib/bootstrap_form/inputs/inputs_collection.rb
index 9d742255..b1a57149 100644
--- a/lib/bootstrap_form/inputs/inputs_collection.rb
+++ b/lib/bootstrap_form/inputs/inputs_collection.rb
@@ -32,7 +32,7 @@ def group_label_class(field_layout)
       end
 
       # FIXME: Find a way to reduce the parameter list size
-      # rubocop:disable Metrics/ParameterLists
+      # rubocop:disable-next Metrics/ParameterLists
       def form_group_collection_input_options(options, text, obj, index, input_value, collection)
         input_options = options.merge(label: text.respond_to?(:call) ? text.call(obj) : obj.send(text))
         if (checked = input_options[:checked])
@@ -46,7 +46,6 @@ def form_group_collection_input_options(options, text, obj, index, input_value,
         input_options.except!(:class)
         input_options
       end
-      # rubocop:enable Metrics/ParameterLists
 
       def form_group_collection_input_checked?(checked, obj, input_value)
         checked == input_value || Array(checked).try(:include?, input_value) ||
diff --git a/test/test_helper.rb b/test/test_helper.rb
index da0547aa..aa9c3c47 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -2,7 +2,7 @@
 
 ENV["RAILS_ENV"] ||= "test"
 
-puts "BUNDLE_GEMFILE: #{ENV.fetch('BUNDLE_GEMFILE', nil)}" # rubocop:disable Rails/Output
+puts "BUNDLE_GEMFILE: #{ENV.fetch('BUNDLE_GEMFILE', nil)}"
 
 require "warning"
 mail_gem_path = Gem::Specification.find_by_name("mail").full_gem_path