diff --git a/src/Grant/ClientCredentialsGrant.php b/src/Grant/ClientCredentialsGrant.php
index 1ed22b8d..05f6a917 100644
--- a/src/Grant/ClientCredentialsGrant.php
+++ b/src/Grant/ClientCredentialsGrant.php
@@ -34,12 +34,11 @@ class ClientCredentialsGrant extends AbstractGrant
     public function respondToRequest(
         ServerRequestInterface $request,
         ResponseTypeInterface $responseType,
-        \DateInterval $tokenTTL,
-        $scopeDelimiter = ' '
+        \DateInterval $tokenTTL
     ) {
         // Validate request
         $client = $this->validateClient($request);
-        $scopes = $this->validateScopes($this->getRequestParameter('scope', $request), $scopeDelimiter, $client);
+        $scopes = $this->validateScopes($this->getRequestParameter('scope', $request), $client);
 
         // Issue and persist access token
         $accessToken = $this->issueAccessToken($tokenTTL, $client, $client->getIdentifier(), $scopes);
diff --git a/src/Grant/GrantTypeInterface.php b/src/Grant/GrantTypeInterface.php
index fbaa88a1..3b775bfb 100644
--- a/src/Grant/GrantTypeInterface.php
+++ b/src/Grant/GrantTypeInterface.php
@@ -41,15 +41,13 @@ interface GrantTypeInterface
      * @param \Psr\Http\Message\ServerRequestInterface                  $request
      * @param \League\OAuth2\Server\ResponseTypes\ResponseTypeInterface $responseType
      * @param \DateInterval                                             $tokenTTL
-     * @param string                                                    $scopeDelimiter
      *
      * @return \League\OAuth2\Server\ResponseTypes\ResponseTypeInterface
      */
     public function respondToRequest(
         ServerRequestInterface $request,
         ResponseTypeInterface $responseType,
-        DateInterval $tokenTTL,
-        $scopeDelimiter = ' '
+        DateInterval $tokenTTL
     );
 
     /**
diff --git a/src/Grant/PasswordGrant.php b/src/Grant/PasswordGrant.php
index 2ebb5afe..e526384d 100644
--- a/src/Grant/PasswordGrant.php
+++ b/src/Grant/PasswordGrant.php
@@ -59,13 +59,12 @@ class PasswordGrant extends AbstractGrant
     public function respondToRequest(
         ServerRequestInterface $request,
         ResponseTypeInterface $responseType,
-        \DateInterval $tokenTTL,
-        $scopeDelimiter = ' '
+        \DateInterval $tokenTTL
     ) {
         // Validate request
         $client = $this->validateClient($request);
         $user = $this->validateUser($request);
-        $scopes = $this->validateScopes($this->getRequestParameter('scope', $request), $scopeDelimiter, $client);
+        $scopes = $this->validateScopes($this->getRequestParameter('scope', $request), $client);
 
         // Issue and persist new tokens
         $accessToken = $this->issueAccessToken($tokenTTL, $client, $user->getIdentifier(), $scopes);
diff --git a/src/Grant/RefreshTokenGrant.php b/src/Grant/RefreshTokenGrant.php
index f9869b59..21fe4f39 100644
--- a/src/Grant/RefreshTokenGrant.php
+++ b/src/Grant/RefreshTokenGrant.php
@@ -58,12 +58,11 @@ class RefreshTokenGrant extends AbstractGrant
     public function respondToRequest(
         ServerRequestInterface $request,
         ResponseTypeInterface $responseType,
-        \DateInterval $tokenTTL,
-        $scopeDelimiter = ' '
+        \DateInterval $tokenTTL
     ) {
         $client = $this->validateClient($request);
         $oldRefreshToken = $this->validateOldRefreshToken($request, $client->getIdentifier());
-        $scopes = $this->validateScopes($this->getRequestParameter('scope', $request), $scopeDelimiter, $client);
+        $scopes = $this->validateScopes($this->getRequestParameter('scope', $request), $client);
 
         // If no new scopes are requested then give the access token the original session scopes
         if (count($scopes) === 0) {