diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 798a52f9e52..d3aee3f1ddf 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -97,7 +97,17 @@ jobs:
           #
           bundler-cache: true
       - name: Run RSpec
-        run: bundle exec rspec
+        run: bundle exec rspec --format progress
+      - name: Install dependencies for appraisals
+        run: bundle exec appraisal install
+      - name: Run RSpec with Rails 5.2
+        run: bundle exec appraisal rails_5.2 rspec --format progress --require rails_helper
+      - name: Run RSpec with Rails 6.0
+        run: bundle exec appraisal rails_6.0 rspec --format progress --require rails_helper
+      - name: Run RSpec with Rails 6.1
+        run: bundle exec appraisal rails_6.1 rspec --format progress --require rails_helper
+      - name: Run RSpec with Rails 7.0
+        run: bundle exec appraisal rails_7.0 rspec --format progress --require rails_helper
       ##
       # NOTE: `lcov-result-merger' is written in JS.
       #
@@ -113,7 +123,7 @@ jobs:
       # https://stackoverflow.com/questions/70742968/automatically-accept-installing-npx-package
       #
       - name: Merge coverage reports into single file
-        run: npx --yes lcov-result-merger ./coverage/**/lcov.info ./coverage/lcov.info
+        run: npx --yes lcov-result-merger 'coverage/rails_7.0/lcov.info' 'coverage/lcov.info' && cat coverage/lcov.info
       - name: Configure coverage reports for Coveralls
         uses: coverallsapp/github-action@master
         with:
diff --git a/Appraisals b/Appraisals
index 04b78000e39..02ce573dbd7 100644
--- a/Appraisals
+++ b/Appraisals
@@ -1,18 +1,24 @@
 # frozen_string_literal: true
 
-appraise "rails-5" do
-  gem "activemodel", "~> 5.0.0"
+appraise "rails_5.2" do
+  gem "activemodel", "~> 5.2.0"
 
   gem "shoulda-matchers", "~> 4.0.0"
 end
 
-appraise "rails-6" do
+appraise "rails_6.0" do
   gem "activemodel", "~> 6.0.0"
 
   gem "shoulda-matchers", "~> 5.0.0"
 end
 
-appraise "rails-7" do
+appraise "rails_6.1" do
+  gem "activemodel", "~> 6.1.0"
+
+  gem "shoulda-matchers", "~> 5.0.0"
+end
+
+appraise "rails_7.0" do
   gem "activemodel", "~> 7.0.0"
 
   gem "shoulda-matchers", "~> 5.0.0"
diff --git a/lib/convenient_service/common/plugins/has_attributes/using_active_model_attributes/patches/active_model_attributes.rb b/lib/convenient_service/common/plugins/has_attributes/using_active_model_attributes/patches/active_model_attributes.rb
index 7a51628b92e..9c0d3d281cc 100644
--- a/lib/convenient_service/common/plugins/has_attributes/using_active_model_attributes/patches/active_model_attributes.rb
+++ b/lib/convenient_service/common/plugins/has_attributes/using_active_model_attributes/patches/active_model_attributes.rb
@@ -12,7 +12,12 @@ module UsingActiveModelAttributes
           module Patches
             ##
             # Copy of `ActiveModel::Attributes'.
-            # https://api.rubyonrails.org/classes/ActiveModel/Attributes/ClassMethods.html
+            # - https://api.rubyonrails.org/classes/ActiveModel/Attributes/ClassMethods.html
+            #
+            # - https://github.com/rails/rails/blob/v7.0.0/activemodel/lib/active_model/attributes.rb
+            # - https://github.com/rails/rails/blob/v6.1.0/activemodel/lib/active_model/attributes.rbhttps://github.com/rails/rails/blob/v6.1.0/activemodel/lib/active_model/attributes.rb
+            # - https://github.com/rails/rails/blob/v6.0.0/activemodel/lib/active_model/attributes.rb
+            # - https://github.com/rails/rails/blob/v5.2.0/activemodel/lib/active_model/attributes.rb
             #
             ActiveModelAttributes =
               ::ActiveModel::Attributes.dup.tap do |mod|
diff --git a/spec/lib/convenient_service/service/plugins/has_result_params_validations/using_active_model_validations/middleware_spec.rb b/spec/lib/convenient_service/service/plugins/has_result_params_validations/using_active_model_validations/middleware_spec.rb
index 55e7e6d5f70..f7e09ee35d0 100644
--- a/spec/lib/convenient_service/service/plugins/has_result_params_validations/using_active_model_validations/middleware_spec.rb
+++ b/spec/lib/convenient_service/service/plugins/has_result_params_validations/using_active_model_validations/middleware_spec.rb
@@ -40,7 +40,27 @@ class self::Internals
 
           attr_reader :foo
 
-          validates :foo, length: {maximum: 2}
+          ##
+          # NOTE: Rails 6 and 7 differently handle nested hashes in `validates' call. See links below.
+          # - https://github.com/rails/rails/blob/v6.0.0/activemodel/lib/active_model/translation.rb#L67
+          # - https://github.com/rails/rails/blob/v7.0.0/activemodel/lib/active_model/translation.rb#L67
+          # - https://github.com/rails/rails/commit/4645f2d34fc1d9f037096de988e5cc5ca41a3cf3
+          #
+          # For example, the following works in Ruby 2.7 + Rails 6, Ruby 2.7 + Rails 7, Ruby 3.* + Rails 7,
+          # but fails in Ruby 3.* and Rails 6.
+          #   validates :foo, length: {maximum: 2}
+          #
+          # To imitate a similar behaviour in Rails 6 a custom validation can be used.
+          #   validate { errors.add(:foo, "Foo length is over 2") if foo.to_s.length > 2 }
+          #   validate_with LengthValidatior, fields: :foo
+          #
+          # More info:
+          # - https://guides.rubyonrails.org/active_record_validations.html#performing-custom-validations
+          #
+          # TODO: Add to troubleshoting.
+          #
+          # validates :foo, length: {maximum: 2}
+          validate { errors.add(:foo, "Foo length is over 2") if foo.to_s.length > 2 }
 
           def initialize(foo:)
             @foo = foo