diff --git a/src/OAuth2/Grant/GrantTypeInterface.php b/src/OAuth2/Grant/GrantTypeInterface.php
index e1902400..f64b3e9f 100644
--- a/src/OAuth2/Grant/GrantTypeInterface.php
+++ b/src/OAuth2/Grant/GrantTypeInterface.php
@@ -12,21 +12,6 @@ use OAuth2\Storage\ScopeInterface;
 
 interface GrantTypeInterface
 {
-	/**
-	 * The grant type identifier
-	 * @var string
-	 */
-	protected $identifier = '';
-
-	/**
-	 * The response type
-	 *
-	 * This is not used for most grant types
-	 *
-	 * @var null|string
-	 */
-	protected $responseType = null;
-
 	/**
 	 * Returns the grant identifier (used to validate grant_type in OAuth2\AuthServer\issueAccessToken())
 	 * @return string