diff --git a/src/Exception/InvalidClientException.php b/src/Exception/InvalidClientException.php
index c09b70b5..ba01d277 100644
--- a/src/Exception/InvalidClientException.php
+++ b/src/Exception/InvalidClientException.php
@@ -29,7 +29,7 @@ class InvalidClientException extends OAuthException
     /**
      * {@inheritdoc}
      */
-    public function __construct($parameter)
+    public function __construct()
     {
         parent::__construct('Client authentication failed.');
     }
diff --git a/src/Exception/InvalidCredentialsException.php b/src/Exception/InvalidCredentialsException.php
index 0aae7431..40c4ce7e 100644
--- a/src/Exception/InvalidCredentialsException.php
+++ b/src/Exception/InvalidCredentialsException.php
@@ -29,8 +29,8 @@ class InvalidCredentialsException extends OAuthException
     /**
      * {@inheritdoc}
      */
-    public function __construct($parameter)
+    public function __construct()
     {
-        parent::__construct('The user credentials were incorrect..');
+        parent::__construct('The user credentials were incorrect.');
     }
 }
diff --git a/src/Exception/InvalidRefreshException.php b/src/Exception/InvalidRefreshException.php
index c1fd1bd5..5c116f84 100644
--- a/src/Exception/InvalidRefreshException.php
+++ b/src/Exception/InvalidRefreshException.php
@@ -29,7 +29,7 @@ class InvalidRefreshException extends OAuthException
     /**
      * {@inheritdoc}
      */
-    public function __construct($parameter)
+    public function __construct()
     {
         parent::__construct('The refresh token is invalid.');
     }
diff --git a/src/Grant/AuthCode.php b/src/Grant/AuthCode.php
index b374b07e..b0980a72 100644
--- a/src/Grant/AuthCode.php
+++ b/src/Grant/AuthCode.php
@@ -101,7 +101,7 @@ class AuthCode extends AbstractGrant
 
         // Ensure response type is one that is recognised
         if ( ! in_array($responseType, $this->server->getResponseTypes())) {
-            throw new Exception\UnsupportedResponseTypeException();
+            throw new Exception\UnsupportedResponseTypeException($responseType);
         }
 
         // Validate client ID and redirect URI
diff --git a/src/Grant/ClientCredentials.php b/src/Grant/ClientCredentials.php
index 655fafac..2c4e38d9 100644
--- a/src/Grant/ClientCredentials.php
+++ b/src/Grant/ClientCredentials.php
@@ -16,7 +16,7 @@ use League\OAuth2\Server\Entity\AccessToken;
 use League\OAuth2\Server\Entity\Client;
 use League\OAuth2\Server\Entity\Session;
 use League\OAuth2\Server\Entity\Scope;
-use League\OAuth2\Server\Exception\ClientException;
+use League\OAuth2\Server\Exception;
 use League\OAuth2\Server\Util\SecureKey;
 use League\OAuth2\Server\Storage\SessionInterface;
 use League\OAuth2\Server\Storage\ClientInterface;
@@ -61,18 +61,12 @@ class ClientCredentials extends AbstractGrant
          // Get the required params
         $clientId = $this->server->getRequest()->request->get('client_id', null);
         if (is_null($clientId)) {
-            throw new ClientException(
-                sprintf(AuthorizationServer::getExceptionMessage('invalid_request'), 'client_id'),
-                0
-            );
+            throw new Exception\InvalidRequestException('client_id');
         }
 
         $clientSecret = $this->server->getRequest()->request->get('client_secret', null);
         if (is_null($clientSecret)) {
-            throw new ClientException(
-                sprintf(AuthorizationServer::getExceptionMessage('invalid_request'), 'client_secret'),
-                0
-            );
+            throw new Exception\InvalidRequestException('client_secret');
         }
 
         // Validate client ID and client secret
@@ -84,7 +78,7 @@ class ClientCredentials extends AbstractGrant
         );
 
         if (($client instanceof Client) === false) {
-            throw new ClientException(AuthorizationServer::getExceptionMessage('invalid_client'), 8);
+            throw new Exception\InvalidClientException();
         }
 
         // Validate any scopes that are in the request
diff --git a/src/Grant/Password.php b/src/Grant/Password.php
index 7dcc083c..baaff116 100644
--- a/src/Grant/Password.php
+++ b/src/Grant/Password.php
@@ -17,8 +17,7 @@ use League\OAuth2\Server\Entity\Client;
 use League\OAuth2\Server\Entity\RefreshToken as RT;
 use League\OAuth2\Server\Entity\Session;
 use League\OAuth2\Server\Entity\Scope;
-use League\OAuth2\Server\Exception\ClientException;
-use League\OAuth2\Server\Exception\InvalidGrantTypeException;
+use League\OAuth2\Server\Exception;
 use League\OAuth2\Server\Util\SecureKey;
 use League\OAuth2\Server\Storage\SessionInterface;
 use League\OAuth2\Server\Storage\ClientInterface;
@@ -70,7 +69,7 @@ class Password extends AbstractGrant
     protected function getVerifyCredentialsCallback()
     {
         if (is_null($this->callback) || ! is_callable($this->callback)) {
-            throw new InvalidGrantTypeException('Null or non-callable callback set on Password grant');
+            throw new Exception\ServerErrorException('Null or non-callable callback set on Password grant');
         }
 
         return $this->callback;
@@ -86,18 +85,12 @@ class Password extends AbstractGrant
         // Get the required params
         $clientId = $this->server->getRequest()->request->get('client_id', null);
         if (is_null($clientId)) {
-            throw new ClientException(
-                sprintf(AuthorizationServer::getExceptionMessage('invalid_request'), 'client_id'),
-                0
-            );
+            throw new Exception\InvalidRequestException('client_id');
         }
 
         $clientSecret = $this->server->getRequest()->request->get('client_secret', null);
         if (is_null($clientSecret)) {
-            throw new ClientException(
-                sprintf(AuthorizationServer::getExceptionMessage('invalid_request'), 'client_secret'),
-                0
-            );
+            throw new Exception\InvalidRequestException('client_secret');
         }
 
         // Validate client ID and client secret
@@ -109,30 +102,24 @@ class Password extends AbstractGrant
         );
 
         if (($client instanceof Client) === false) {
-            throw new ClientException(AuthorizationServer::getExceptionMessage('invalid_client'), 8);
+            throw new Exception\InvalidClientException();
         }
 
         $username = $this->server->getRequest()->request->get('username', null);
         if (is_null($username)) {
-            throw new ClientException(
-                sprintf(AuthorizationServer::getExceptionMessage('invalid_request'), 'username'),
-                0
-            );
+            throw new Exception\InvalidRequestException('username');
         }
 
         $password = $this->server->getRequest()->request->get('password', null);
         if (is_null($password)) {
-            throw new ClientException(
-                sprintf(AuthorizationServer::getExceptionMessage('invalid_request'), 'password'),
-                0
-            );
+            throw new Exception\InvalidRequestException('password');
         }
 
         // Check if user's username and password are correct
         $userId = call_user_func($this->getVerifyCredentialsCallback(), $username, $password);
 
         if ($userId === false) {
-            throw new ClientException($this->server->getExceptionMessage('invalid_credentials'), 0);
+            throw new Exception\InvalidCredentialsException();
         }
 
         // Validate any scopes that are in the request
diff --git a/src/Grant/RefreshToken.php b/src/Grant/RefreshToken.php
index b1993161..80e514f4 100644
--- a/src/Grant/RefreshToken.php
+++ b/src/Grant/RefreshToken.php
@@ -21,7 +21,6 @@ use League\OAuth2\Server\Storage\ScopeInterface;
 use League\OAuth2\Server\Entity\RefreshToken as RT;
 use League\OAuth2\Server\Entity\AccessToken;
 use League\OAuth2\Server\Entity\Session;
-use League\OAuth2\Server\Exception\ClientException;
 
 /**
  * Referesh token grant
@@ -65,18 +64,12 @@ class RefreshToken extends AbstractGrant
     {
         $clientId = $this->server->getRequest()->request->get('client_id', null);
         if (is_null($clientId)) {
-            throw new Exception\ClientException(
-                sprintf($this->server->getExceptionMessage('invalid_request'), 'client_id'),
-                0
-            );
+            throw new Exception\InvalidRequestException('client_id');
         }
 
         $clientSecret = $this->server->getRequest()->request->get('client_secret', null);
         if (is_null($clientSecret)) {
-            throw new Exception\ClientException(
-                sprintf($this->server->getExceptionMessage('invalid_request'), 'client_secret'),
-                0
-            );
+            throw new Exception\InvalidRequestException('client_secret');
         }
 
         // Validate client ID and client secret
@@ -88,22 +81,19 @@ class RefreshToken extends AbstractGrant
         );
 
         if ($client === null) {
-            throw new ClientException(AuthorizationServer::getExceptionMessage('invalid_client'), 8);
+            throw new Exception\InvalidClientException();
         }
 
         $oldRefreshTokenParam = $this->server->getRequest()->request->get('refresh_token', null);
         if ($oldRefreshTokenParam === null) {
-            throw new Exception\ClientException(
-                sprintf($this->server->getExceptionMessage('invalid_request'), 'refresh_token'),
-                0
-            );
+            throw new Exception\InvalidRequestException('refresh_token');
         }
 
         // Validate refresh token
         $oldRefreshToken = $this->server->getStorage('refresh_token')->get($oldRefreshTokenParam);
 
         if (($oldRefreshToken instanceof RT) === false) {
-            throw new Exception\ClientException($this->server->getExceptionMessage('invalid_refresh'), 0);
+            throw new Exception\InvalidRefreshException();
         }
 
         $oldAccessToken = $oldRefreshToken->getAccessToken();
@@ -124,10 +114,7 @@ class RefreshToken extends AbstractGrant
             //  the request doesn't include any new scopes
             foreach ($requestedScopes as $requestedScope) {
                 if (!isset($scopes[$requestedScope->getId()])) {
-                    throw new Exception\ClientException(
-                        sprintf($this->server->getExceptionMessage('invalid_scope'), $requestedScope->getId()),
-                        0
-                    );
+                    throw new Exception\InvalidScopeException($requestedScope->getId());
                 }
             }
 
diff --git a/src/ResourceServer.php b/src/ResourceServer.php
index 35ed1e37..f3723dbf 100644
--- a/src/ResourceServer.php
+++ b/src/ResourceServer.php
@@ -210,7 +210,7 @@ class ResourceServer extends AbstractServer
         }
 
         if (empty($accessToken)) {
-            throw new Exception\InvalidAccessTokenException('Access token is missing');
+            throw new Exception\InvalidRequestException('access token');
         }
 
         return $accessToken;