imap-backup.gemspec in imap-backup-2.2.1 vs imap-backup.gemspec in imap-backup-2.2.2

@@ -11,10 +11,10 @@
 
   gem.files         = `git ls-files`.split($OUTPUT_RECORD_SEPARATOR)
   gem.executables   = gem.files.grep(%r{^bin/}).map { |f| File.basename(f) }
   gem.test_files    = gem.files.grep(%r{^spec/})
   gem.require_paths = ["lib"]
-  gem.required_ruby_version = [">= 2.3.0"]
+  gem.required_ruby_version = [">= 2.4.0"]
   gem.version = Imap::Backup::VERSION
 
   gem.post_install_message = <<-MESSAGE.gsub(/^\s{4}/m, "")
     Note that, when upgrading #{gem.name} from version 1.x to 2.x,
     the metadata storage method has changed (from flat file to JSON).