diff --git a/rb/lib/twitter-text/extractor.rb b/rb/lib/twitter-text/extractor.rb
index a2fd7db7b..25734fe58 100644
--- a/rb/lib/twitter-text/extractor.rb
+++ b/rb/lib/twitter-text/extractor.rb
@@ -3,7 +3,7 @@
 # http://www.apache.org/licenses/LICENSE-2.0
 
 # encoding: utf-8
-require 'idn'
+require 'simpleidn'
 
 class String
   # Helper function to count the character length by first converting to an
@@ -57,6 +57,8 @@ module Extractor extend self
       # Maximum URL length as defined by Twitter's backend.
       MAX_URL_LENGTH = 4096
 
+      MAX_DOMAIN_LABEL_LENGTH = 63
+
       # The maximum t.co path length that the Twitter backend supports.
       MAX_TCO_SLUG_LENGTH = 40
 
@@ -373,7 +375,12 @@ def is_valid_domain(url_length, domain, protocol)
         begin
           raise ArgumentError.new("invalid empty domain") unless domain
           original_domain_length = domain.length
-          encoded_domain = IDN::Idna.toASCII(domain)
+          encoded_domain = SimpleIDN.to_ascii(domain)
+          # If the domain starts with xn-- but is not only ASCII characters, it's invalid.
+          return false if domain.start_with?("xn--") && !domain.ascii_only?
+          labels = encoded_domain.split('.')
+          # If any label of the domain is longer than 63 characters, it's invalid.
+          return false if labels.any?{|label| label.length > MAX_DOMAIN_LABEL_LENGTH}
           updated_domain_length = encoded_domain.length
           url_length += (updated_domain_length - original_domain_length) if (updated_domain_length > original_domain_length)
           url_length += URL_PROTOCOL_LENGTH unless protocol
diff --git a/rb/spec/test_urls.rb b/rb/spec/test_urls.rb
index dc2b5c7ff..942194f3a 100644
--- a/rb/spec/test_urls.rb
+++ b/rb/spec/test_urls.rb
@@ -41,7 +41,9 @@ module TestUrls
     "http://foobar.中国",
     "http://foobar.پاکستان",
     "https://www.youtube.com/playlist?list=PL0ZPu8XSRTB7wZzn0mLHMvyzVFeRxbWn-",
-    "http://ああ.com"
+    "http://ああ.com",
+    "twitter.联通",
+    "https://🌈🌈🌈.st"
   ] unless defined?(TestUrls::VALID)
 
   INVALID = [
diff --git a/rb/twitter-text.gemspec b/rb/twitter-text.gemspec
index e145b6362..2eef1410c 100644
--- a/rb/twitter-text.gemspec
+++ b/rb/twitter-text.gemspec
@@ -19,14 +19,13 @@ Gem::Specification.new do |s|
 
   s.add_development_dependency "test-unit"
   s.add_development_dependency "multi_json", "~> 1.3"
-  s.add_development_dependency "nokogiri", "~> 1.10.9"
+  s.add_development_dependency "nokogiri", "~> 1.15.3"
   s.add_development_dependency "rake"
   s.add_development_dependency "rdoc"
   s.add_development_dependency "rspec", "~> 3.0"
   s.add_development_dependency "simplecov"
   s.add_runtime_dependency     "unf", "~> 0.1.0"
-  # Use of idn-ruby requires libidn to be installed separately
-  s.add_runtime_dependency     "idn-ruby"
+  s.add_runtime_dependency     "simpleidn"
 
   s.files         = `git ls-files`.split("\n") + ['lib/assets/tld_lib.yml'] + Dir['config/*']
   s.test_files    = `git ls-files -- {test,spec,features}/*`.split("\n")