diff --git a/src/CredentialsLoader.php b/src/CredentialsLoader.php
index 6ab4d4e11..bd347f9f1 100644
--- a/src/CredentialsLoader.php
+++ b/src/CredentialsLoader.php
@@ -28,7 +28,7 @@
  */
 abstract class CredentialsLoader implements FetchAuthTokenInterface
 {
-  const TOKEN_CREDENTIAL_URI = 'https://www.googleapis.com/oauth2/v3/token';
+  const TOKEN_CREDENTIAL_URI = 'https://www.googleapis.com/oauth2/v4/token';
   const ENV_VAR = 'GOOGLE_APPLICATION_CREDENTIALS';
   const WELL_KNOWN_PATH = 'gcloud/application_default_credentials.json';
   const NON_WINDOWS_WELL_KNOWN_PATH_BASE = '.config';