diff --git a/src/Entities/AuthCodeEntityInterface.php b/src/Entities/AuthCodeEntityInterface.php
index f1033af1..00e939c2 100644
--- a/src/Entities/AuthCodeEntityInterface.php
+++ b/src/Entities/AuthCodeEntityInterface.php
@@ -17,7 +17,7 @@ interface AuthCodeEntityInterface extends TokenInterface
     public function getRedirectUri();
 
     /**
-     * @param string|null $uri
+     * @param string $uri
      */
     public function setRedirectUri($uri);
 }
diff --git a/src/Grant/AbstractGrant.php b/src/Grant/AbstractGrant.php
index 53b2853d..79a1ac47 100644
--- a/src/Grant/AbstractGrant.php
+++ b/src/Grant/AbstractGrant.php
@@ -407,7 +407,10 @@ abstract class AbstractGrant implements GrantTypeInterface
         $authCode->setExpiryDateTime((new \DateTime())->add($authCodeTTL));
         $authCode->setClient($client);
         $authCode->setUserIdentifier($userIdentifier);
-        $authCode->setRedirectUri($redirectUri);
+
+        if ($redirectUri !== null) {
+            $authCode->setRedirectUri($redirectUri);
+        }
 
         foreach ($scopes as $scope) {
             $authCode->addScope($scope);
diff --git a/src/Grant/AuthCodeGrant.php b/src/Grant/AuthCodeGrant.php
index d1669b2f..81152338 100644
--- a/src/Grant/AuthCodeGrant.php
+++ b/src/Grant/AuthCodeGrant.php
@@ -270,7 +270,11 @@ class AuthCodeGrant extends AbstractAuthorizeGrant
         $authorizationRequest->setGrantTypeId($this->getIdentifier());
         $authorizationRequest->setClient($client);
         $authorizationRequest->setRedirectUri($redirectUri);
-        $authorizationRequest->setState($stateParameter);
+
+        if ($stateParameter !== null) {
+            $authorizationRequest->setState($stateParameter);
+        }
+
         $authorizationRequest->setScopes($scopes);
 
         if ($this->enableCodeExchangeProof === true) {
diff --git a/src/Grant/ImplicitGrant.php b/src/Grant/ImplicitGrant.php
index 19e3e684..80c34869 100644
--- a/src/Grant/ImplicitGrant.php
+++ b/src/Grant/ImplicitGrant.php
@@ -177,7 +177,11 @@ class ImplicitGrant extends AbstractAuthorizeGrant
         $authorizationRequest->setGrantTypeId($this->getIdentifier());
         $authorizationRequest->setClient($client);
         $authorizationRequest->setRedirectUri($redirectUri);
-        $authorizationRequest->setState($stateParameter);
+
+        if ($stateParameter !== null) {
+            $authorizationRequest->setState($stateParameter);          
+        }
+
         $authorizationRequest->setScopes($finalizedScopes);
 
         return $authorizationRequest;
diff --git a/src/RequestTypes/AuthorizationRequest.php b/src/RequestTypes/AuthorizationRequest.php
index 150c920b..5faa45d4 100644
--- a/src/RequestTypes/AuthorizationRequest.php
+++ b/src/RequestTypes/AuthorizationRequest.php
@@ -183,7 +183,7 @@ class AuthorizationRequest
     }
 
     /**
-     * @param string|null $state
+     * @param string $state
      */
     public function setState($state)
     {