diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2d837bd..15b957d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 ## CHANGELOG
 
+### 2.4.0
+* Update Rack install documentation
+* Update Lists API endpoint for checking list subscriptions
+
 ### 2.3.0
 
 * Added ability to set API key in request without setting Klaviyo.private_api_key
diff --git a/README.md b/README.md
index f9bb493..54230c7 100644
--- a/README.md
+++ b/README.md
@@ -414,7 +414,7 @@ To automatically insert the Klaviyo script in your Rails app, add this to your e
 
 ```ruby
 require 'rack/klaviyo'
-config.middleware.use "Klaviyo::Client::Middleware", "YOUR_PUBLIC_KLAVIYO_API_TOKEN"
+config.middleware.use Rack::Klaviyo, "YOUR_PUBLIC_KLAVIYO_API_TOKEN"
 ```
 
 This will automatically insert the Klaviyo script at the bottom on your HTML page, right before the closing `body` tag.
diff --git a/klaviyo.gemspec b/klaviyo.gemspec
index 48ee04a..e7a5329 100644
--- a/klaviyo.gemspec
+++ b/klaviyo.gemspec
@@ -2,8 +2,8 @@ files = ['klaviyo.gemspec', '{lib}/**/**/*'].map {|f| Dir[f]}.flatten
 
 Gem::Specification.new do |s|
   s.name        = 'klaviyo'
-  s.version     = '2.3.0'
-  s.date        = '2021-10-28'
+  s.version     = '2.4.0'
+  s.date        = '2021-12-06'
   s.summary     = 'You heard us, a Ruby wrapper for the Klaviyo API'
   s.description = 'Ruby wrapper for the Klaviyo API'
   s.authors     = ['Klaviyo Team']
diff --git a/lib/klaviyo/apis/lists.rb b/lib/klaviyo/apis/lists.rb
index 62f55c4..7a0a2cd 100644
--- a/lib/klaviyo/apis/lists.rb
+++ b/lib/klaviyo/apis/lists.rb
@@ -6,6 +6,7 @@ class Lists < Client
     LISTS = 'lists'
     MEMBERS = 'members'
     SUBSCRIBE = 'subscribe'
+    GET_LIST_SUBSCRIPTIONS = 'get-list-subscriptions'
 
     # Creates a new list
     # @param list_name [String] the list name
@@ -65,13 +66,13 @@ def self.delete_list(list_id, api_key: nil)
     # @return A list of JSON objects of the profiles. Profiles that are
     #   supressed or not found are not included.
     def self.check_list_subscriptions(list_id, api_key: nil, emails: [], phone_numbers: [], push_tokens: [])
-      path = "#{LIST}/#{list_id}/#{SUBSCRIBE}"
+      path = "#{LIST}/#{list_id}/#{GET_LIST_SUBSCRIPTIONS}"
       params = {
         :emails => emails,
         :phone_numbers => phone_numbers,
         :push_tokens => push_tokens
       }
-      v2_request(HTTP_GET, path, api_key: api_key, **params)
+      v2_request(HTTP_POST, path, api_key: api_key, **params)
     end
 
     # Subscribe profiles to a list.
diff --git a/lib/klaviyo/client.rb b/lib/klaviyo/client.rb
index 07000bb..61a26c4 100644
--- a/lib/klaviyo/client.rb
+++ b/lib/klaviyo/client.rb
@@ -4,7 +4,7 @@ class Client
     V1_API = 'v1'
     V2_API = 'v2'
 
-    KL_VERSION = '2.3.0'
+    KL_VERSION = '2.4.0'
     KL_USER_AGENT = "Ruby_Klaviyo/#{KL_VERSION}"
 
     HTTP_DELETE = 'delete'
diff --git a/lib/rack/klaviyo.rb b/lib/rack/klaviyo.rb
index 2ac9309..cd70c75 100644
--- a/lib/rack/klaviyo.rb
+++ b/lib/rack/klaviyo.rb
@@ -26,8 +26,8 @@ def call(env)
     def update_response!
       @response.each do |part|
         insert_at = part.index(@options[:insert_js_last] ? '</body' : '</head')
-        unless insert_at.nil?
-          part.insert(insert_at, render_script)
+        unless insert_at.nil? || part.frozen?
+          part.insert(insert_at, render_script.html_safe)
         end
       end
     end