Gemfile in asciidoctor-epub3-1.5.0.alpha.12 vs Gemfile in asciidoctor-epub3-1.5.0.alpha.13

@@ -6,9 +6,14 @@
 gemspec
 
 gem 'asciidoctor', ENV['ASCIIDOCTOR_VERSION'], require: false if ENV.key? 'ASCIIDOCTOR_VERSION'
 
 group :optional do
+  # epubcheck-ruby might be safe to be converted into runtime dependency, but could have issues when packaged into asciidoctorj-epub3
+  gem 'epubcheck-ruby', '~> 4.2.2.0'
+  # We would like to make kindlegen a runtime dependency, but can't because of the way asciidoctorj-epub3 packaging works
+  # See https://github.com/asciidoctor/asciidoctor-epub3/issues/288
+  gem 'kindlegen', '~> 3.0.3'
   gem 'pygments.rb', '1.2.1'
 end
 
 group :docs do
   gem 'yard', require: false