diff --git a/index.js b/index.js
index 5448b93..b45c2dc 100644
--- a/index.js
+++ b/index.js
@@ -22,6 +22,8 @@ app.use(
 );
 app.use(morgan("combined"));
 
+const removeNullValues = (obj) => Object.entries(obj).reduce((a,[k,v]) => (v ? (a[k]=v, a) : a), {})
+
 const getMcpClient = async () => {
   const mcpIssuer = await Issuer.discover(process.env.MCP_PROVIDER);
 
@@ -79,12 +81,12 @@ const getAuthorizationControllerFactory = (extraParams) => {
       req.session.state = state;
       req.session.nonce = nonce;
 
-      const redirectUrl = client.authorizationUrl({
+      const redirectUrl = client.authorizationUrl(removeNullValues({
         nonce,
         state,
         ...AUTHORIZATION_DEFAULT_PARAMS,
         ...extraParams,
-      });
+      }));
 
       res.redirect(redirectUrl);
     } catch (e) {
diff --git a/views/index.ejs b/views/index.ejs
index b5edf6c..8a21f86 100644
--- a/views/index.ejs
+++ b/views/index.ejs
@@ -96,7 +96,16 @@
                     cols="50"
                     rows="12"
                 ><%= locals.defaultParamsValue %></textarea>
-                <br>
+                <p>
+                    La liste des paramètres utilisables est disponible dans la
+                    <a
+                            href="https://github.com/panva/openid-client/blob/v5.x/docs/README.md#clientauthorizationurlparameters"
+                            target="_blank"
+                            rel="noopener noreferrer"
+                    >
+                        librairie oidc-client
+                    </a>.
+                </p>
                 <button id="custom-connection">Connexion personnalisée</button>
             </form>
         </details>