diff --git a/ext/readline/readline-ext.gemspec b/ext/readline/readline-ext.gemspec
new file mode 100644
index 0000000000..a611a8ea9a
--- /dev/null
+++ b/ext/readline/readline-ext.gemspec
@@ -0,0 +1,21 @@
+Gem::Specification.new do |spec|
+  spec.name          = "readline-ext"
+  spec.version       = "0.1.0"
+  spec.authors       = ["Yukihiro Matsumoto"]
+  spec.email         = ["matz@ruby-lang.org"]
+
+  spec.summary       = %q{Provides an interface for GNU Readline and Edit Line (libedit).}
+  spec.description   = %q{Provides an interface for GNU Readline and Edit Line (libedit).}
+  spec.homepage      = "https://github.com/ruby/readline-ext"
+  spec.license       = "BSD-2-Clause"
+
+  spec.metadata["homepage_uri"] = spec.homepage
+  spec.metadata["source_code_uri"] = spec.homepage
+
+  spec.files         = Dir.chdir(File.expand_path('..', __FILE__)) do
+    `git ls-files -z`.split("\x0").reject { |f| f.match(%r{^(test|spec|features)/}) }
+  end
+  spec.bindir        = "exe"
+  spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
+  spec.require_paths = ["lib"]
+end
diff --git a/tool/sync_default_gems.rb b/tool/sync_default_gems.rb
index 3cd9177e63..cdf55cd9b9 100644
--- a/tool/sync_default_gems.rb
+++ b/tool/sync_default_gems.rb
@@ -43,6 +43,7 @@
 # * https://github.com/ruby/net-smtp
 # * https://github.com/ruby/cgi
 # * https://github.com/ruby/readline
+# * https://github.com/ruby/readline-ext
 #
 
 require 'fileutils'
@@ -93,6 +94,7 @@ $repositories = {
   netsmtp: "ruby/net-smtp",
   cgi: "ruby/cgi",
   readline: "ruby/readline",
+  readlineext: "ruby/readline-ext"
 }
 
 def sync_default_gems(gem)
@@ -243,6 +245,9 @@ def sync_default_gems(gem)
   when "netsmtp"
     sync_lib "net-smtp"
     mv "lib/net-smtp.gemspec", "lib/net/smtp"
+  when "readlineext"
+    sync_lib "readline-ext"
+    mv "lib/readline-ext.gemspec", "ext/readline"
   else
     sync_lib gem
   end