diff --git a/src/League/OAuth2/Server/Authorization.php b/src/League/OAuth2/Server/Authorization.php
index 1e6f53db..216b165a 100644
--- a/src/League/OAuth2/Server/Authorization.php
+++ b/src/League/OAuth2/Server/Authorization.php
@@ -426,7 +426,7 @@ class Authorization
     /**
      * Return a grant type class
      * @param  string $grantType The grant type identifer
-     * @return class
+     * @return Grant\AuthCode|Grant\ClientCredentials|Grant\Implict|Grant\Password|Grant\RefreshToken
      */
     public function getGrantType($grantType)
     {
diff --git a/src/League/OAuth2/Server/Grant/Password.php b/src/League/OAuth2/Server/Grant/Password.php
index d56e481a..45e6c0ee 100644
--- a/src/League/OAuth2/Server/Grant/Password.php
+++ b/src/League/OAuth2/Server/Grant/Password.php
@@ -94,7 +94,8 @@ class Password implements GrantTypeInterface {
 
     /**
      * Set the callback to verify a user's username and password
-     * @param function $callback The callback function
+     * @param callable $callback The callback function
+     * @return void
      */
     public function setVerifyCredentialsCallback($callback)
     {
@@ -103,7 +104,7 @@ class Password implements GrantTypeInterface {
 
     /**
      * Return the callback function
-     * @return function
+     * @return callable
      */
     protected function getVerifyCredentialsCallback()
     {
diff --git a/src/League/OAuth2/Server/Grant/RefreshToken.php b/src/League/OAuth2/Server/Grant/RefreshToken.php
index 0a9c3d92..fe62291d 100644
--- a/src/League/OAuth2/Server/Grant/RefreshToken.php
+++ b/src/League/OAuth2/Server/Grant/RefreshToken.php
@@ -56,7 +56,7 @@ class RefreshToken implements GrantTypeInterface {
 
     /**
      * Constructor
-     * @param AuthServer $authServer AuthServer instance
+     * @param Authorization $authServer Authorization server instance
      * @return void
      */
     public function __construct(Authorization $authServer)