diff --git a/lib/API/API.php b/lib/API/API.php
index e1f768c838..29071a46ce 100644
--- a/lib/API/API.php
+++ b/lib/API/API.php
@@ -10,13 +10,13 @@ class API {
   public $endpoint;
   public $action;
   public $data;
-  const API_NAME = 'mailpoet_api';
+  const NAME = 'mailpoet_api';
   const ENDPOINT_NAMESPACE = '\MailPoet\API\Endpoints\\';
-  const API_RESPONSE_CODE_ERROR = 404;
+  const RESPONSE_ERROR = 404;
 
   function __construct($api_data = false) {
     $api_data = ($api_data) ? $api_data : $_GET;
-    $this->api_request = isset($api_data[self::API_NAME]);
+    $this->api_request = isset($api_data[self::NAME]);
     $this->endpoint = isset($api_data['endpoint']) ?
       Helpers::underscoreToCamelCase($api_data['endpoint']) :
       false;
@@ -32,7 +32,7 @@ class API {
     $endpoint = self::ENDPOINT_NAMESPACE . ucfirst($this->endpoint);
     if(!$this->api_request) return;
     if(!$this->endpoint || !class_exists($endpoint)) {
-      $this->terminateRequest(self::API_RESPONSE_CODE_ERROR, __('Invalid API endpoint.'));
+      $this->terminateRequest(self::RESPONSE_ERROR, __('Invalid API endpoint.'));
     }
     $this->callEndpoint(
       $endpoint,
@@ -43,7 +43,7 @@ class API {
 
   function callEndpoint($endpoint, $action, $data) {
     if(!method_exists($endpoint, $action)) {
-      $this->terminateRequest(self::API_RESPONSE_CODE_ERROR, __('Invalid API action.'));
+      $this->terminateRequest(self::RESPONSE_ERROR, __('Invalid API action.'));
     }
     call_user_func(
       array(
@@ -58,7 +58,7 @@ class API {
     $data = base64_decode($data);
     return (is_serialized($data)) ?
       unserialize($data) :
-      self::terminateRequest(self::API_RESPONSE_CODE_ERROR, __('Invalid API data format.'));
+      self::terminateRequest(self::RESPONSE_ERROR, __('Invalid API data format.'));
   }
 
   static function encodeRequestData($data) {
@@ -68,7 +68,7 @@ class API {
   static function buildRequest($endpoint, $action, $data) {
     $data = self::encodeRequestData($data);
     $params = array(
-      self::API_NAME => '',
+      self::NAME => '',
       'endpoint' => $endpoint,
       'action' => $action,
       'data' => $data
diff --git a/lib/Subscription/Url.php b/lib/Subscription/Url.php
index 64bddba41d..52e6045f14 100644
--- a/lib/Subscription/Url.php
+++ b/lib/Subscription/Url.php
@@ -45,7 +45,7 @@ class Url {
     }
 
     $params = array(
-      API::API_NAME,
+      API::NAME,
       'endpoint='.Subscription::ENDPOINT,
       'action='.$action,
       'data='.API::encodeRequestData($data)