diff --git a/README.md b/README.md
index b0331d2c..58faccd1 100644
--- a/README.md
+++ b/README.md
@@ -199,7 +199,7 @@ $resource = LTI\LTI_Deep_Link_Resource::new()
 
 Everything is set to return the resource to the platform. There are two methods of doing this.
 
-The following method will output the html for an aut-posting form for you.
+The following method will output the html for an auto-posting form for you.
 ```php
 $dl->output_response_form([$resource]);
 ```
@@ -209,6 +209,12 @@ Alternatively you can just request the signed JWT that will need posting back to
 $dl->get_response_jwt([$resource]);
 ```
 
+If you've created a JWKS endpoint with `LTI\JWKS_Endpoint::new()`, the kid used in the endpoint can be provided as an additional parameter.
+```php
+$dl->get_response_jwt([$resource], 'a_unique_KID');
+
+```
+
 ## Calling Services
 ### Names and Roles Service
 
diff --git a/src/lti/LTI_Deep_Link.php b/src/lti/LTI_Deep_Link.php
index c87cb0da..06631a04 100644
--- a/src/lti/LTI_Deep_Link.php
+++ b/src/lti/LTI_Deep_Link.php
@@ -14,10 +14,10 @@ public function __construct($registration, $deployment_id, $deep_link_settings)
         $this->deep_link_settings = $deep_link_settings;
     }
 
-    public function get_response_jwt($resources) {
+    public function get_response_jwt($resources, string $kid = null) {
         $message_jwt = [
             "iss" => $this->registration->get_client_id(),
-            "aud" => [$this->registration->get_issuer()],
+            "aud" => $this->registration->get_issuer(),
             "exp" => time() + 600,
             "iat" => time(),
             "nonce" => 'nonce' . hash('sha256', random_bytes(64)),
@@ -27,11 +27,17 @@ public function get_response_jwt($resources) {
             "https://purl.imsglobal.org/spec/lti-dl/claim/content_items" => array_map(function($resource) { return $resource->to_array(); }, $resources),
             "https://purl.imsglobal.org/spec/lti-dl/claim/data" => $this->deep_link_settings['data'],
         ];
-        return JWT::encode($message_jwt, $this->registration->get_tool_private_key(), 'RS256', $this->registration->get_kid());
+
+        return JWT::encode(
+            $message_jwt,
+            $this->registration->get_tool_private_key(),
+            'RS256',
+            is_null($kid) ?  $this->registration->get_kid() : $kid
+        );
     }
 
-    public function output_response_form($resources) {
-        $jwt = $this->get_response_jwt($resources);
+    public function output_response_form($resources, string $kid = null) {
+        $jwt = $this->get_response_jwt($resources, $kid);
         ?>
         <form id="auto_submit" action="<?= $this->deep_link_settings['deep_link_return_url']; ?>" method="POST">
             <input type="hidden" name="JWT" value="<?= $jwt ?>" />
diff --git a/src/lti/LTI_Deep_Link_Resource.php b/src/lti/LTI_Deep_Link_Resource.php
index 8abeadd6..b9215275 100644
--- a/src/lti/LTI_Deep_Link_Resource.php
+++ b/src/lti/LTI_Deep_Link_Resource.php
@@ -76,8 +76,11 @@ public function to_array() {
             "presentation" => [
                 "documentTarget" => $this->target,
             ],
-            "custom" => $this->custom_params,
         ];
+        if (count($this->custom_params) > 0) {
+            $resource["custom"] = $this->custom_params;
+        }
+
         if ($this->lineitem !== null) {
             $resource["lineItem"] = [
                 "scoreMaximum" => $this->lineitem->get_score_maximum(),
diff --git a/src/lti/LTI_Message_Launch.php b/src/lti/LTI_Message_Launch.php
index 7a18195d..4997a700 100644
--- a/src/lti/LTI_Message_Launch.php
+++ b/src/lti/LTI_Message_Launch.php
@@ -3,6 +3,7 @@
 
 use Firebase\JWT\JWK;
 use Firebase\JWT\JWT;
+use Firebase\JWT\Key;
 
 JWT::$leeway = 5;
 
@@ -220,7 +221,7 @@ private function get_public_key() {
         foreach ($public_key_set['keys'] as $key) {
             if ($key['kid'] == $this->jwt['header']['kid']) {
                 try {
-                    return openssl_pkey_get_details(JWK::parseKey($key));
+                    return openssl_pkey_get_details(JWK::parseKey($key, 'RS256')->getKeyMaterial());
                 } catch(\Exception $e) {
                     return false;
                 }
@@ -299,7 +300,7 @@ private function validate_jwt_signature() {
 
         // Validate JWT signature
         try {
-            JWT::decode($this->request['id_token'], $public_key['key'], array('RS256'));
+            JWT::decode($this->request['id_token'], new Key($public_key['key'], 'RS256'));
         } catch(\Exception $e) {
             var_dump($e);
             // Error validating signature.