diff --git a/src/Grant/AuthCodeGrant.php b/src/Grant/AuthCodeGrant.php
index d6411237..acd2f381 100644
--- a/src/Grant/AuthCodeGrant.php
+++ b/src/Grant/AuthCodeGrant.php
@@ -273,7 +273,8 @@ class AuthCodeGrant extends AbstractGrant
         // Generate the access token
         $accessToken = new AccessTokenEntity($this->server);
         $accessToken->setIdentifier(SecureKey::generate());
-        $accessToken->setExpiryDateTime((new \DateTime)->add($accessTokenTTL));
+        $expirationDateTime = (new \DateTime())->add($accessTokenTTL);
+        $accessToken->setExpiryDateTime($expirationDateTime);
         $accessToken->setClient($client);
 
         foreach ($code->getScopes() as $scope) {
diff --git a/src/Grant/ClientCredentialsGrant.php b/src/Grant/ClientCredentialsGrant.php
index 39cab779..50be9a1f 100644
--- a/src/Grant/ClientCredentialsGrant.php
+++ b/src/Grant/ClientCredentialsGrant.php
@@ -82,7 +82,8 @@ class ClientCredentialsGrant extends AbstractGrant
         // Generate an access token
         $accessToken = new AccessTokenEntity();
         $accessToken->setIdentifier(SecureKey::generate());
-        $accessToken->setExpiryDateTime((new \DateTime())->add($accessTokenTTL));
+        $expirationDateTime = (new \DateTime())->add($accessTokenTTL);
+        $accessToken->setExpiryDateTime($expirationDateTime);
         $accessToken->setClient($client);
         $accessToken->setOwner('client', $client->getIdentifier());
 
diff --git a/src/Grant/PasswordGrant.php b/src/Grant/PasswordGrant.php
index c29c867c..e50f4708 100644
--- a/src/Grant/PasswordGrant.php
+++ b/src/Grant/PasswordGrant.php
@@ -147,7 +147,8 @@ class PasswordGrant extends AbstractGrant
         // Generate an access token
         $accessToken = new AccessTokenEntity();
         $accessToken->setIdentifier(SecureKey::generate());
-        $accessToken->setExpiryDateTime((new \DateTime())->add($accessTokenTTL));
+        $expirationDateTime = (new \DateTime())->add($accessTokenTTL);
+        $accessToken->setExpiryDateTime($expirationDateTime);
         $accessToken->setOwner('user', $user->getIdentifier());
         $accessToken->setClient($client);