diff --git a/index.d.ts b/index.d.ts
index e1604ab..fdc8465 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -26,7 +26,7 @@ export interface FastifyBasicAuthOptions {
     reply: FastifyReply,
     done: (err?: Error) => void
   ): void | Promise<void|Error>;
-  authenticate?: boolean | { realm: string };
+  authenticate?: boolean | { realm: string | ((req: FastifyRequest) => string) };
   header?: string;
 }
 
diff --git a/index.test-d.ts b/index.test-d.ts
index 3937a28..e24a56c 100644
--- a/index.test-d.ts
+++ b/index.test-d.ts
@@ -49,6 +49,26 @@ app.register(fastifyBasicAuth, {
   }
 })
 
+//authenticate boolean
+app.register(fastifyBasicAuth, {
+  validate: () => {},
+  authenticate: true
+})
+
+//authenticate with realm
+app.register(fastifyBasicAuth, {
+  validate: () => {},
+  authenticate: { realm: 'example' }
+})
+
+//authenticate with realm (function)
+app.register(fastifyBasicAuth, {
+  validate: () => {},
+  authenticate: { realm: function realm(req) {
+    return req.routerPath
+  }}
+})
+
 expectAssignable<onRequestHookHandler>(app.basicAuth)
 expectAssignable<preValidationHookHandler>(app.basicAuth)
 expectAssignable<preHandlerHookHandler>(app.basicAuth)