diff --git a/src/OAuth2/ResourceServer.php b/src/OAuth2/ResourceServer.php
index 195f98ed..474b1635 100644
--- a/src/OAuth2/ResourceServer.php
+++ b/src/OAuth2/ResourceServer.php
@@ -163,15 +163,15 @@ class ResourceServer
      */
     public function isValid()
     {
-        $access_token = $this->determineAccessToken();
+        $accessToken = $this->determineAccessToken();
 
-        $result = $this->storages['session']->validateAccessToken($access_token);
+        $result = $this->storages['session']->validateAccessToken($accessToken);
 
         if ( ! $result) {
             throw new Exception\InvalidAccessTokenException('Access token is not valid');
         }
 
-        $this->accessToken = $access_token;
+        $this->accessToken = $accessToken;
         $this->sessionId = $result['id'];
         $this->ownerType = $result['owner_type'];
         $this->ownerId = $result['owner_id'];
@@ -215,17 +215,17 @@ class ResourceServer
     protected function determineAccessToken()
     {
         if ($header = $this->getRequest()->header('Authorization')) {
-            $access_token = trim(str_replace('Bearer', '', $header));
+            $accessToken = trim(str_replace('Bearer', '', $header));
         } else {
             $method = $this->getRequest()->server('REQUEST_METHOD');
-            $access_token = $this->getRequest()->{$method}($this->tokenKey);
+            $accessToken = $this->getRequest()->{$method}($this->tokenKey);
         }
 
-        if (empty($access_token)) {
+        if (empty($accessToken)) {
             throw new Exception\InvalidAccessTokenException('Access token is missing');
         }
 
-        return $access_token;
+        return $accessToken;
     }
 
 }