diff --git a/Gemfile b/Gemfile
index 2511623..32e19bb 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 source 'https://rubygems.org'
 
 # Specify your gem's dependencies in test_gem.gemspec
diff --git a/Rakefile b/Rakefile
index cb60140..7eb6825 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'bundler/gem_tasks'
 require 'rspec/core/rake_task'
 require 'rubocop/rake_task'
diff --git a/exe/letsencrypt_webfaction b/exe/letsencrypt_webfaction
index 484a7fc..1e9cce0 100755
--- a/exe/letsencrypt_webfaction
+++ b/exe/letsencrypt_webfaction
@@ -1,4 +1,5 @@
 #!/usr/bin/env ruby
+# frozen_string_literal: true
 
 require 'letsencrypt_webfaction/application'
 require 'letsencrypt_webfaction/errors'
diff --git a/letsencrypt_webfaction.gemspec b/letsencrypt_webfaction.gemspec
index a90b448..54834ee 100644
--- a/letsencrypt_webfaction.gemspec
+++ b/letsencrypt_webfaction.gemspec
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 lib = File.expand_path('lib', __dir__)
 $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
 require 'letsencrypt_webfaction'
diff --git a/lib/letsencrypt_webfaction.rb b/lib/letsencrypt_webfaction.rb
index ba47b70..34dc748 100644
--- a/lib/letsencrypt_webfaction.rb
+++ b/lib/letsencrypt_webfaction.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module LetsencryptWebfaction
-  VERSION = '4.0.0'.freeze
+  VERSION = '4.0.0'
 end
diff --git a/lib/letsencrypt_webfaction/application.rb b/lib/letsencrypt_webfaction/application.rb
index ed689a8..0fb715e 100644
--- a/lib/letsencrypt_webfaction/application.rb
+++ b/lib/letsencrypt_webfaction/application.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'letsencrypt_webfaction/application/init'
 require 'letsencrypt_webfaction/application/run'
 require 'letsencrypt_webfaction/application/version'
diff --git a/lib/letsencrypt_webfaction/application/init.rb b/lib/letsencrypt_webfaction/application/init.rb
index e1cab97..4fcefce 100644
--- a/lib/letsencrypt_webfaction/application/init.rb
+++ b/lib/letsencrypt_webfaction/application/init.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'letsencrypt_webfaction/options'
 
 require 'pathname'
diff --git a/lib/letsencrypt_webfaction/application/run.rb b/lib/letsencrypt_webfaction/application/run.rb
index 055c164..55f8e80 100644
--- a/lib/letsencrypt_webfaction/application/run.rb
+++ b/lib/letsencrypt_webfaction/application/run.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'letsencrypt_webfaction/options'
 require 'letsencrypt_webfaction/errors'
 require 'letsencrypt_webfaction/webfaction_api_credentials'
diff --git a/lib/letsencrypt_webfaction/application/version.rb b/lib/letsencrypt_webfaction/application/version.rb
index 596d91c..8624cd4 100644
--- a/lib/letsencrypt_webfaction/application/version.rb
+++ b/lib/letsencrypt_webfaction/application/version.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'letsencrypt_webfaction'
 
 module LetsencryptWebfaction
diff --git a/lib/letsencrypt_webfaction/certificate_installer.rb b/lib/letsencrypt_webfaction/certificate_installer.rb
index 9bfb4bd..fe50f2e 100644
--- a/lib/letsencrypt_webfaction/certificate_installer.rb
+++ b/lib/letsencrypt_webfaction/certificate_installer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'xmlrpc/client'
 
 module LetsencryptWebfaction
diff --git a/lib/letsencrypt_webfaction/certificate_issuer.rb b/lib/letsencrypt_webfaction/certificate_issuer.rb
index 912e172..6dfa37f 100644
--- a/lib/letsencrypt_webfaction/certificate_issuer.rb
+++ b/lib/letsencrypt_webfaction/certificate_issuer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'acme-client'
 require 'letsencrypt_webfaction/domain_validator'
 require 'letsencrypt_webfaction/certificate_installer'
diff --git a/lib/letsencrypt_webfaction/domain_validator.rb b/lib/letsencrypt_webfaction/domain_validator.rb
index 3b2ab5f..3c98108 100644
--- a/lib/letsencrypt_webfaction/domain_validator.rb
+++ b/lib/letsencrypt_webfaction/domain_validator.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'fileutils'
 
 module LetsencryptWebfaction
diff --git a/lib/letsencrypt_webfaction/errors.rb b/lib/letsencrypt_webfaction/errors.rb
index 9853bfa..28c2524 100644
--- a/lib/letsencrypt_webfaction/errors.rb
+++ b/lib/letsencrypt_webfaction/errors.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module LetsencryptWebfaction
   class Error < StandardError; end
   class InvalidConfigValueError < Error; end
diff --git a/lib/letsencrypt_webfaction/logger_output.rb b/lib/letsencrypt_webfaction/logger_output.rb
index 6ef479e..d3e4ee3 100644
--- a/lib/letsencrypt_webfaction/logger_output.rb
+++ b/lib/letsencrypt_webfaction/logger_output.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module LetsencryptWebfaction
   class LoggerOutput
     attr_accessor :quiet
diff --git a/lib/letsencrypt_webfaction/options.rb b/lib/letsencrypt_webfaction/options.rb
index a66ada8..810dc8b 100644
--- a/lib/letsencrypt_webfaction/options.rb
+++ b/lib/letsencrypt_webfaction/options.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'toml-rb'
 require 'socket'
 
@@ -7,7 +9,7 @@ module LetsencryptWebfaction
   class Options
     NON_BLANK_FIELDS = %i[username password letsencrypt_account_email directory api_url servername].freeze
 
-    WEBFACTION_API_URL = 'https://api.webfaction.com/'.freeze
+    WEBFACTION_API_URL = 'https://api.webfaction.com/'
 
     def initialize(args)
       @config = args
diff --git a/lib/letsencrypt_webfaction/options/certificate.rb b/lib/letsencrypt_webfaction/options/certificate.rb
index 2eb0ac1..ad1d62a 100644
--- a/lib/letsencrypt_webfaction/options/certificate.rb
+++ b/lib/letsencrypt_webfaction/options/certificate.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module LetsencryptWebfaction
   class Options
     class Certificate
diff --git a/lib/letsencrypt_webfaction/webfaction_api_credentials.rb b/lib/letsencrypt_webfaction/webfaction_api_credentials.rb
index 78aad5f..ee4292b 100644
--- a/lib/letsencrypt_webfaction/webfaction_api_credentials.rb
+++ b/lib/letsencrypt_webfaction/webfaction_api_credentials.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'xmlrpc/client'
 
 module LetsencryptWebfaction
diff --git a/spec/lib/letsencrypt_webfaction/application/init_spec.rb b/spec/lib/letsencrypt_webfaction/application/init_spec.rb
index 2d9bfbc..1d7f383 100644
--- a/spec/lib/letsencrypt_webfaction/application/init_spec.rb
+++ b/spec/lib/letsencrypt_webfaction/application/init_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'letsencrypt_webfaction/application/init'
 
 RSpec.describe LetsencryptWebfaction::Application::Init, :uses_tmp_dir do
diff --git a/spec/lib/letsencrypt_webfaction/application/run_spec.rb b/spec/lib/letsencrypt_webfaction/application/run_spec.rb
index baa3e99..0f2eb36 100644
--- a/spec/lib/letsencrypt_webfaction/application/run_spec.rb
+++ b/spec/lib/letsencrypt_webfaction/application/run_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'acme-client'
 require 'xmlrpc/client'
 require 'letsencrypt_webfaction/application/run'
diff --git a/spec/lib/letsencrypt_webfaction/application/version_spec.rb b/spec/lib/letsencrypt_webfaction/application/version_spec.rb
index 4270ef8..ec77af9 100644
--- a/spec/lib/letsencrypt_webfaction/application/version_spec.rb
+++ b/spec/lib/letsencrypt_webfaction/application/version_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'letsencrypt_webfaction/application/version'
 
 RSpec.describe LetsencryptWebfaction::Application::Version do
diff --git a/spec/lib/letsencrypt_webfaction/application_spec.rb b/spec/lib/letsencrypt_webfaction/application_spec.rb
index 698002d..c46feee 100644
--- a/spec/lib/letsencrypt_webfaction/application_spec.rb
+++ b/spec/lib/letsencrypt_webfaction/application_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'letsencrypt_webfaction/application'
 
 RSpec.describe LetsencryptWebfaction::Application do
diff --git a/spec/lib/letsencrypt_webfaction/certificate_installer_spec.rb b/spec/lib/letsencrypt_webfaction/certificate_installer_spec.rb
index cfc39e4..3e34613 100644
--- a/spec/lib/letsencrypt_webfaction/certificate_installer_spec.rb
+++ b/spec/lib/letsencrypt_webfaction/certificate_installer_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'letsencrypt_webfaction/certificate_installer'
 require 'letsencrypt_webfaction/webfaction_api_credentials'
 
diff --git a/spec/lib/letsencrypt_webfaction/certificate_issuer_spec.rb b/spec/lib/letsencrypt_webfaction/certificate_issuer_spec.rb
index 2f7ff90..45364ac 100644
--- a/spec/lib/letsencrypt_webfaction/certificate_issuer_spec.rb
+++ b/spec/lib/letsencrypt_webfaction/certificate_issuer_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'letsencrypt_webfaction/certificate_issuer'
 require 'letsencrypt_webfaction/webfaction_api_credentials'
 require 'letsencrypt_webfaction/options/certificate'
diff --git a/spec/lib/letsencrypt_webfaction/domain_validator_spec.rb b/spec/lib/letsencrypt_webfaction/domain_validator_spec.rb
index 72ed36b..07b1d67 100644
--- a/spec/lib/letsencrypt_webfaction/domain_validator_spec.rb
+++ b/spec/lib/letsencrypt_webfaction/domain_validator_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'acme/client'
 require 'letsencrypt_webfaction/domain_validator'
 
diff --git a/spec/lib/letsencrypt_webfaction/options/certificate_spec.rb b/spec/lib/letsencrypt_webfaction/options/certificate_spec.rb
index 0e45110..263c5ba 100644
--- a/spec/lib/letsencrypt_webfaction/options/certificate_spec.rb
+++ b/spec/lib/letsencrypt_webfaction/options/certificate_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'letsencrypt_webfaction/options/certificate'
 require 'letsencrypt_webfaction/errors'
 
diff --git a/spec/lib/letsencrypt_webfaction/options_spec.rb b/spec/lib/letsencrypt_webfaction/options_spec.rb
index 70646e6..c02c89d 100644
--- a/spec/lib/letsencrypt_webfaction/options_spec.rb
+++ b/spec/lib/letsencrypt_webfaction/options_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'letsencrypt_webfaction/options'
 
 RSpec.describe LetsencryptWebfaction::Options do
diff --git a/spec/lib/letsencrypt_webfaction/webfaction_api_credentials_spec.rb b/spec/lib/letsencrypt_webfaction/webfaction_api_credentials_spec.rb
index b0f2775..55cb3f3 100644
--- a/spec/lib/letsencrypt_webfaction/webfaction_api_credentials_spec.rb
+++ b/spec/lib/letsencrypt_webfaction/webfaction_api_credentials_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'letsencrypt_webfaction/webfaction_api_credentials'
 
 RSpec.describe LetsencryptWebfaction::WebfactionApiCredentials do
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 21b5a43..898baa6 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Add lib to the require dir.
 $LOAD_PATH.unshift(File.dirname(__FILE__) + '/../lib')
 
diff --git a/spec/support/fixtures.rb b/spec/support/fixtures.rb
index a132ba1..a786ed3 100644
--- a/spec/support/fixtures.rb
+++ b/spec/support/fixtures.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 def fixture(filename)
   FIXTURE_DIR.join(filename).read
 end