diff --git a/src/Grant/ImplicitGrant.php b/src/Grant/ImplicitGrant.php
index 62a48147..2ec9aed7 100644
--- a/src/Grant/ImplicitGrant.php
+++ b/src/Grant/ImplicitGrant.php
@@ -95,8 +95,8 @@ class ImplicitGrant extends AbstractAuthorizeGrant
     public function canRespondToAuthorizationRequest(ServerRequestInterface $request)
     {
         return (
-            array_key_exists('response_type', $request->getQueryParams())
-            && $request->getQueryParams()['response_type'] === 'token'
+            isset($request->getQueryParams()['response_type'])
+            && 'token' === $request->getQueryParams()['response_type']
             && isset($request->getQueryParams()['client_id'])
         );
     }