diff --git a/sql/mysql.sql b/sql/mysql.sql
index e66b2205..552b5e02 100644
--- a/sql/mysql.sql
+++ b/sql/mysql.sql
@@ -38,12 +38,13 @@ CREATE TABLE `oauth_session_access_tokens` (
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
 
 CREATE TABLE `oauth_session_authcodes` (
+  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
   `session_id` int(10) unsigned NOT NULL,
   `auth_code` char(40) NOT NULL,
   `auth_code_expires` int(10) unsigned NOT NULL,
-  `scope_ids` char(255) DEFAULT NULL,
-  PRIMARY KEY (`session_id`),
-  CONSTRAINT `f_oaseau_seid` FOREIGN KEY (`session_id`) REFERENCES `oauth_sessions` (`id`) ON DELETE CASCADE ON UPDATE NO ACTION
+  PRIMARY KEY (`id`),
+  KEY `session_id` (`session_id`),
+  CONSTRAINT `oauth_session_authcodes_ibfk_1` FOREIGN KEY (`session_id`) REFERENCES `oauth_sessions` (`id`) ON DELETE CASCADE
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
 
 CREATE TABLE `oauth_session_redirects` (
@@ -70,7 +71,7 @@ CREATE TABLE `oauth_scopes` (
   `name` varchar(255) NOT NULL,
   `description` varchar(255) DEFAULT NULL,
   PRIMARY KEY (`id`),
-  UNIQUE KEY `u_oasc_sc` (`scope_key`)
+  UNIQUE KEY `u_oasc_sc` (`scope`)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
 
 CREATE TABLE `oauth_session_token_scopes` (
@@ -82,4 +83,13 @@ CREATE TABLE `oauth_session_token_scopes` (
   KEY `f_oasetosc_scid` (`scope_id`),
   CONSTRAINT `f_oasetosc_scid` FOREIGN KEY (`scope_id`) REFERENCES `oauth_scopes` (`id`) ON DELETE CASCADE ON UPDATE NO ACTION,
   CONSTRAINT `f_oasetosc_setoid` FOREIGN KEY (`session_access_token_id`) REFERENCES `oauth_session_access_tokens` (`id`) ON DELETE CASCADE ON UPDATE NO ACTION
+) ENGINE=InnoDB DEFAULT CHARSET=utf8;
+
+CREATE TABLE `oauth_session_authcode_scopes` (
+  `oauth_session_authcode_id` int(10) unsigned NOT NULL,
+  `scope_id` smallint(5) unsigned NOT NULL,
+  KEY `oauth_session_authcode_id` (`oauth_session_authcode_id`),
+  KEY `scope_id` (`scope_id`),
+  CONSTRAINT `oauth_session_authcode_scopes_ibfk_2` FOREIGN KEY (`scope_id`) REFERENCES `oauth_scopes` (`id`) ON DELETE CASCADE,
+  CONSTRAINT `oauth_session_authcode_scopes_ibfk_1` FOREIGN KEY (`oauth_session_authcode_id`) REFERENCES `oauth_session_authcodes` (`id`) ON DELETE CASCADE
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
\ No newline at end of file
diff --git a/src/League/OAuth2/Server/Grant/AuthCode.php b/src/League/OAuth2/Server/Grant/AuthCode.php
index b8837099..70447a41 100644
--- a/src/League/OAuth2/Server/Grant/AuthCode.php
+++ b/src/League/OAuth2/Server/Grant/AuthCode.php
@@ -193,13 +193,6 @@ class AuthCode implements GrantTypeInterface {
         // Remove any old sessions the user might have
         $this->authServer->getStorage('session')->deleteSession($authParams['client_id'], $type, $typeId);
 
-        // List of scopes IDs
-        $scopeIds = array();
-        foreach ($authParams['scopes'] as $scope)
-        {
-            $scopeIds[] = $scope['id'];
-        }
-
         // Create a new session
         $sessionId = $this->authServer->getStorage('session')->createSession($authParams['client_id'], $type, $typeId);
 
@@ -207,7 +200,12 @@ class AuthCode implements GrantTypeInterface {
         $this->authServer->getStorage('session')->associateRedirectUri($sessionId, $authParams['redirect_uri']);
 
         // Associate the auth code
-        $this->authServer->getStorage('session')->associateAuthCode($sessionId, $authCode, time() + $this->authTokenTTL, implode(',', $scopeIds));
+        $authCodeId = $this->authServer->getStorage('session')->associateAuthCode($sessionId, $authCode, time() + $this->authTokenTTL);
+
+        // Associate the scopes to the auth code
+        foreach ($authParams['scopes'] as $scope) {
+            $this->authServer->getStorage('session')->associateAuthCodeScope($authCodeId, $scope['id']);
+        }
 
         return $authCode;
     }
@@ -249,30 +247,30 @@ class AuthCode implements GrantTypeInterface {
         }
 
         // Verify the authorization code matches the client_id and the request_uri
-        $session = $this->authServer->getStorage('session')->validateAuthCode($authParams['client_id'], $authParams['redirect_uri'], $authParams['code']);
+        $authCodeDetails = $this->authServer->getStorage('session')->validateAuthCode($authParams['client_id'], $authParams['redirect_uri'], $authParams['code']);
 
-        if ( ! $session) {
+        if ( ! $authCodeDetails) {
             throw new Exception\ClientException(sprintf($this->authServer->getExceptionMessage('invalid_grant'), 'code'), 9);
         }
 
-        // A session ID was returned so update it with an access token and remove the authorisation code
+        // Get any associated scopes
+        $scopes = $this->authServer->getStorage('session')->getAuthCodeScopes($authCodeDetails['authcode_id']);
 
+        // A session ID was returned so update it with an access token and remove the authorisation code
         $accessToken = SecureKey::make();
         $accessTokenExpiresIn = ($this->accessTokenTTL !== null) ? $this->accessTokenTTL : $this->authServer->getAccessTokenTTL();
         $accessTokenExpires = time() + $accessTokenExpiresIn;
 
         // Remove the auth code
-        $this->authServer->getStorage('session')->removeAuthCode($session['id']);
+        $this->authServer->getStorage('session')->removeAuthCode($authCodeDetails['session_id']);
 
         // Create an access token
-        $accessTokenId = $this->authServer->getStorage('session')->associateAccessToken($session['id'], $accessToken, $accessTokenExpires);
+        $accessTokenId = $this->authServer->getStorage('session')->associateAccessToken($authCodeDetails['session_id'], $accessToken, $accessTokenExpires);
 
         // Associate scopes with the access token
-        if ( ! is_null($session['scope_ids'])) {
-            $scopeIds = explode(',', $session['scope_ids']);
-
-            foreach ($scopeIds as $scopeId) {
-                $this->authServer->getStorage('session')->associateScope($accessTokenId, $scopeId);
+        if (count($scopes) > 0) {
+            foreach ($scopes as $scope) {
+                $this->authServer->getStorage('session')->associateScope($accessTokenId, $scope['scope_id']);
             }
         }
 
diff --git a/src/League/OAuth2/Server/Storage/PDO/Session.php b/src/League/OAuth2/Server/Storage/PDO/Session.php
index 311ce3f1..abde8b2b 100644
--- a/src/League/OAuth2/Server/Storage/PDO/Session.php
+++ b/src/League/OAuth2/Server/Storage/PDO/Session.php
@@ -70,17 +70,18 @@ class Session implements SessionInterface
         $stmt->execute();
     }
 
-    public function associateAuthCode($sessionId, $authCode, $expireTime, $scopeIds = null)
+    public function associateAuthCode($sessionId, $authCode, $expireTime)
     {
         $db = \ezcDbInstance::get();
 
-        $stmt = $db->prepare('INSERT INTO oauth_session_authcodes (session_id, auth_code, auth_code_expires, scope_ids)
-         VALUE (:sessionId, :authCode, :authCodeExpires, :scopeIds)');
+        $stmt = $db->prepare('INSERT INTO oauth_session_authcodes (session_id, auth_code, auth_code_expires)
+         VALUE (:sessionId, :authCode, :authCodeExpires)');
         $stmt->bindValue(':sessionId', $sessionId);
         $stmt->bindValue(':authCode', $authCode);
         $stmt->bindValue(':authCodeExpires', $expireTime);
-        $stmt->bindValue(':scopeIds', $scopeIds);
         $stmt->execute();
+
+        return $db->lastInsertId();
     }
 
     public function removeAuthCode($sessionId)
@@ -96,12 +97,12 @@ class Session implements SessionInterface
     {
         $db = \ezcDbInstance::get();
 
-        $stmt = $db->prepare('SELECT oauth_sessions.id, oauth_session_authcodes.scope_ids FROM oauth_sessions JOIN
-         oauth_session_authcodes ON oauth_session_authcodes.`session_id` = oauth_sessions.id JOIN
-          oauth_session_redirects ON oauth_session_redirects.`session_id` = oauth_sessions.id WHERE
-           oauth_sessions.client_id = :clientId AND oauth_session_authcodes.`auth_code` = :authCode AND
-            `oauth_session_authcodes`.`auth_code_expires` >= :time AND `oauth_session_redirects`.`redirect_uri`
-             = :redirectUri');
+        $stmt = $db->prepare('SELECT oauth_sessions.id AS session_id, oauth_session_authcodes.id AS authcode_id
+         FROM oauth_sessions JOIN oauth_session_authcodes ON oauth_session_authcodes.`session_id`
+          = oauth_sessions.id JOIN oauth_session_redirects ON oauth_session_redirects.`session_id`
+          = oauth_sessions.id WHERE oauth_sessions.client_id = :clientId AND oauth_session_authcodes.`auth_code`
+          = :authCode AND  `oauth_session_authcodes`.`auth_code_expires` >= :time AND
+           `oauth_session_redirects`.`redirect_uri` = :redirectUri');
         $stmt->bindValue(':clientId', $clientId);
         $stmt->bindValue(':redirectUri', $redirectUri);
         $stmt->bindValue(':authCode', $authCode);
@@ -160,6 +161,27 @@ class Session implements SessionInterface
         return ($result === false) ? false : (array) $result;
     }
 
+    public function associateAuthCodeScope($authCodeId, $scopeId)
+    {
+        $db = \ezcDbInstance::get();
+
+        $stmt = $db->prepare('INSERT INTO `oauth_session_authcode_scopes` (`oauth_session_authcode_id`, `scope_id`) VALUES (:authCodeId, :scopeId)');
+        $stmt->bindValue(':authCodeId', $authCodeId);
+        $stmt->bindValue(':scopeId', $scopeId);
+        $stmt->execute();
+    }
+
+    public function getAuthCodeScopes($oauthSessionAuthCodeId)
+    {
+        $db = \ezcDbInstance::get();
+
+        $stmt = $db->prepare('SELECT scope_id FROM `oauth_session_authcode_scopes` WHERE oauth_session_authcode_id = :authCodeId');
+        $stmt->bindValue(':authCodeId', $oauthSessionAuthCodeId);
+        $stmt->execute();
+
+        return $stmt->fetchAll();
+    }
+
     public function associateScope($accessTokenId, $scopeId)
     {
         $db = \ezcDbInstance::get();
diff --git a/src/League/OAuth2/Server/Storage/SessionInterface.php b/src/League/OAuth2/Server/Storage/SessionInterface.php
index 30b0a6e1..08cd4c53 100644
--- a/src/League/OAuth2/Server/Storage/SessionInterface.php
+++ b/src/League/OAuth2/Server/Storage/SessionInterface.php
@@ -102,17 +102,16 @@ interface SessionInterface
      * Example SQL query:
      *
      * <code>
-     * INSERT INTO oauth_session_authcodes (session_id, auth_code, auth_code_expires, scope_ids)
-     *  VALUE (:sessionId, :authCode, :authCodeExpires, :scopeIds)
+     * INSERT INTO oauth_session_authcodes (session_id, auth_code, auth_code_expires)
+     *  VALUE (:sessionId, :authCode, :authCodeExpires)
      * </code>
      *
      * @param  int    $sessionId  The session ID
      * @param  string $authCode   The authorization code
      * @param  int    $expireTime Unix timestamp of the access token expiry time
-     * @param  string $scopeIds   Comma seperated list of scope IDs to be later associated (default = null)
-     * @return void
+     * @return int                The auth code ID
      */
-    public function associateAuthCode($sessionId, $authCode, $expireTime, $scopeIds = null);
+    public function associateAuthCode($sessionId, $authCode, $expireTime);
 
     /**
      * Remove an associated authorization token from a session
@@ -134,7 +133,7 @@ interface SessionInterface
      * Example SQL query:
      *
      * <code>
-     * SELECT oauth_sessions.id, oauth_session_authcodes.scope_ids FROM oauth_sessions
+     * SELECT oauth_sessions.id AS session_id, oauth_session_authcodes.id AS authcode_id FROM oauth_sessions
      *  JOIN oauth_session_authcodes ON oauth_session_authcodes.`session_id` = oauth_sessions.id
      *  JOIN oauth_session_redirects ON oauth_session_redirects.`session_id` = oauth_sessions.id WHERE
      * oauth_sessions.client_id = :clientId AND oauth_session_authcodes.`auth_code` = :authCode
@@ -146,8 +145,8 @@ interface SessionInterface
      *
      * <code>
      * array(
-     *     'id' =>  (int), // the session ID
-     *     'scope_ids'  =>  (string)
+     *     'session_id' =>  (int)
+     *     'authcode_id'  =>  (int)
      * )
      * </code>
      *
@@ -240,6 +239,50 @@ interface SessionInterface
      */
     public function getAccessToken($accessTokenId);
 
+    /**
+     * Associate scopes with an auth code (bound to the session)
+     *
+     * Example SQL query:
+     *
+     * <code>
+     * INSERT INTO `oauth_session_authcode_scopes` (`oauth_session_authcode_id`, `scope_id`) VALUES
+     *  (:authCodeId, :scopeId)
+     * </code>
+     *
+     * @param  int $authCodeId The auth code ID
+     * @param  int $scopeId    The scope ID
+     * @return void
+     */
+    public function associateAuthCodeScope($authCodeId, $scopeId);
+
+    /**
+     * Get the scopes associated with an auth code
+     *
+     * Example SQL query:
+     *
+     * <code>
+     * SELECT scope_id FROM `oauth_session_authcode_scopes` WHERE oauth_session_authcode_id = :authCodeId
+     * </code>
+     *
+     * Expected response:
+     *
+     * <code>
+     * array(
+     *     array(
+     *         'scope_id' => (int)
+     *     ),
+     *     array(
+     *         'scope_id' => (int)
+     *     ),
+     *     ...
+     * )
+     * </code>
+     *
+     * @param  int   $oauthSessionAuthCodeId The session ID
+     * @return array
+     */
+    public function getAuthCodeScopes($oauthSessionAuthCodeId);
+
     /**
      * Associate a scope with an access token
      *
diff --git a/tests/authorization/AuthCodeGrantTest.php b/tests/authorization/AuthCodeGrantTest.php
index 7cec3ded..ee6a5af9 100644
--- a/tests/authorization/AuthCodeGrantTest.php
+++ b/tests/authorization/AuthCodeGrantTest.php
@@ -376,7 +376,8 @@ class Auth_Code_Grant_Test extends PHPUnit_Framework_TestCase
         $this->session->shouldReceive('createSession')->andReturn(1);
         $this->session->shouldReceive('associateScope')->andReturn(null);
         $this->session->shouldReceive('associateRedirectUri')->andReturn(null);
-        $this->session->shouldReceive('associateAuthCode')->andReturn(null);
+        $this->session->shouldReceive('associateAuthCode')->andReturn(1);
+        $this->session->shouldReceive('associateAuthCodeScope')->andReturn(null);
 
         $a = $this->returnDefault();
         $g = new League\OAuth2\Server\Grant\AuthCode($a);
diff --git a/tests/authorization/AuthServerTest.php b/tests/authorization/AuthServerTest.php
index baf0af00..f4bd2db4 100644
--- a/tests/authorization/AuthServerTest.php
+++ b/tests/authorization/AuthServerTest.php
@@ -358,13 +358,14 @@ class Authorization_Server_test extends PHPUnit_Framework_TestCase
         ));
 
         $this->session->shouldReceive('validateAuthCode')->andReturn(array(
-            'id'    =>  1,
-            'scope_ids' =>  '1'
+            'session_id'    =>  1,
+            'authcode_id' =>  1
         ));
         $this->session->shouldReceive('updateSession')->andReturn(null);
         $this->session->shouldReceive('removeAuthCode')->andReturn(null);
         $this->session->shouldReceive('associateAccessToken')->andReturn(1);
         $this->session->shouldReceive('associateScope')->andReturn(null);
+        $this->session->shouldReceive('getAuthCodeScopes')->andReturn(array('scope_id' => 1));
 
         $a = $this->returnDefault();
         $a->addGrantType(new League\OAuth2\Server\Grant\AuthCode($a));
@@ -399,6 +400,8 @@ class Authorization_Server_test extends PHPUnit_Framework_TestCase
         $this->session->shouldReceive('updateSession')->andReturn(null);
         $this->session->shouldReceive('removeAuthCode')->andReturn(null);
         $this->session->shouldReceive('associateAccessToken')->andReturn(1);
+        $this->session->shouldReceive('getAuthCodeScopes')->andReturn(array('scope_id' => 1));
+        $this->session->shouldReceive('associateScope')->andReturn(null);
 
         $a = $this->returnDefault();
         $a->addGrantType(new League\OAuth2\Server\Grant\AuthCode($a));
@@ -436,6 +439,8 @@ class Authorization_Server_test extends PHPUnit_Framework_TestCase
         $this->session->shouldReceive('updateSession')->andReturn(null);
         $this->session->shouldReceive('removeAuthCode')->andReturn(null);
         $this->session->shouldReceive('associateAccessToken')->andReturn(1);
+        $this->session->shouldReceive('getAuthCodeScopes')->andReturn(array('scope_id' => 1));
+        $this->session->shouldReceive('associateScope')->andReturn(null);
 
         $a = $this->returnDefault();
         $grant = new League\OAuth2\Server\Grant\AuthCode($a);
@@ -477,6 +482,8 @@ class Authorization_Server_test extends PHPUnit_Framework_TestCase
         $this->session->shouldReceive('updateSession')->andReturn(null);
         $this->session->shouldReceive('removeAuthCode')->andReturn(null);
         $this->session->shouldReceive('associateAccessToken')->andReturn(1);
+        $this->session->shouldReceive('getAuthCodeScopes')->andReturn(array('scope_id' => 1));
+        $this->session->shouldReceive('associateScope')->andReturn(null);
 
         $a = $this->returnDefault();
         $a->addGrantType(new League\OAuth2\Server\Grant\AuthCode($a));
diff --git a/tests/authorization/RefreshTokenTest.php b/tests/authorization/RefreshTokenTest.php
index 12dad385..f4882454 100644
--- a/tests/authorization/RefreshTokenTest.php
+++ b/tests/authorization/RefreshTokenTest.php
@@ -42,6 +42,8 @@ class Refresh_Token_test extends PHPUnit_Framework_TestCase
         $this->session->shouldReceive('removeAuthCode')->andReturn(null);
         $this->session->shouldReceive('associateAccessToken')->andReturn(1);
         $this->session->shouldReceive('associateRefreshToken')->andReturn(1);
+        $this->session->shouldReceive('associateScope')->andReturn(null);
+        $this->session->shouldReceive('getAuthCodeScopes')->andReturn(array('scope_id' => 1));
 
         $a = $this->returnDefault();
         $a->addGrantType(new League\OAuth2\Server\Grant\AuthCode($a));