Gemfile in asciidoctor-epub3-1.5.0.alpha.19 vs Gemfile in asciidoctor-epub3-1.5.0

@@ -11,7 +11,9 @@
   gem 'asciidoctor-diagram', '1.5.16', require: false if Gem::Version.new(ENV['ASCIIDOCTOR_VERSION']) < Gem::Version.new('2.0.0')
 end
 
 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', '~> 4.2.4.0'
+  gem 'epubcheck-ruby', '~> 4.2.5.0'
+  # Kindlegen is unavailable neither for 64-bit MacOS nor for ARM
+  gem 'kindlegen', '~> 3.1.0' unless RbConfig::CONFIG['host_os'] =~ /darwin/
 end