diff --git a/src/ApplicationDefaultCredentials.php b/src/ApplicationDefaultCredentials.php
index 80437c8c9..d556fac4e 100644
--- a/src/ApplicationDefaultCredentials.php
+++ b/src/ApplicationDefaultCredentials.php
@@ -144,8 +144,6 @@ public static function getMiddleware(
      * @param string|string[] $defaultScope The default scope to use if no
      *   user-defined scopes exist, expressed either as an Array or as a
      *   space-delimited string.
-     * @param string $universeDomain Specifies a universe domain to use for the
-     *   calling client library
      *
      * @return FetchAuthTokenInterface
      * @throws DomainException if no implementation can be obtained.
@@ -156,8 +154,7 @@ public static function getCredentials(
         array $cacheConfig = null,
         CacheItemPoolInterface $cache = null,
         $quotaProject = null,
-        $defaultScope = null,
-        string $universeDomain = null
+        $defaultScope = null
     ) {
         $creds = null;
         $jsonKey = CredentialsLoader::fromEnv()
@@ -182,9 +179,6 @@ public static function getCredentials(
             if ($quotaProject) {
                 $jsonKey['quota_project_id'] = $quotaProject;
             }
-            if ($universeDomain) {
-                $jsonKey['universe_domain'] = $universeDomain;
-            }
             $creds = CredentialsLoader::makeCredentials(
                 $scope,
                 $jsonKey,
@@ -193,7 +187,7 @@ public static function getCredentials(
         } elseif (AppIdentityCredentials::onAppEngine() && !GCECredentials::onAppEngineFlexible()) {
             $creds = new AppIdentityCredentials($anyScope);
         } elseif (self::onGce($httpHandler, $cacheConfig, $cache)) {
-            $creds = new GCECredentials(null, $anyScope, null, $quotaProject, null, $universeDomain);
+            $creds = new GCECredentials(null, $anyScope, null, $quotaProject);
             $creds->setIsOnGce(true); // save the credentials a trip to the metadata server
         }
 
diff --git a/src/Credentials/GCECredentials.php b/src/Credentials/GCECredentials.php
index ed79dbb37..9453088a3 100644
--- a/src/Credentials/GCECredentials.php
+++ b/src/Credentials/GCECredentials.php
@@ -95,11 +95,6 @@ class GCECredentials extends CredentialsLoader implements
      */
     const PROJECT_ID_URI_PATH = 'v1/project/project-id';
 
-    /**
-     * The metadata path of the project ID.
-     */
-    const UNIVERSE_DOMAIN_URI_PATH = 'v1/universe/universe_domain';
-
     /**
      * The header whose presence indicates GCE presence.
      */
@@ -174,11 +169,6 @@ class GCECredentials extends CredentialsLoader implements
      */
     private $serviceAccountIdentity;
 
-    /**
-     * @var string
-     */
-    private ?string $universeDomain;
-
     /**
      * @param Iam $iam [optional] An IAM instance.
      * @param string|string[] $scope [optional] the scope of the access request,
@@ -188,8 +178,6 @@ class GCECredentials extends CredentialsLoader implements
      *   charges associated with the request.
      * @param string $serviceAccountIdentity [optional] Specify a service
      *   account identity name to use instead of "default".
-     * @param string $universeDomain [optional] Specify a universe domain to use
-     *   instead of fetching one from the metadata server.
      */
     public function __construct(
         Iam $iam = null,
@@ -225,7 +213,6 @@ public function __construct(
         $this->tokenUri = $tokenUri;
         $this->quotaProject = $quotaProject;
         $this->serviceAccountIdentity = $serviceAccountIdentity;
-        $this->universeDomain = $universeDomain;
     }
 
     /**
diff --git a/src/Credentials/ServiceAccountCredentials.php b/src/Credentials/ServiceAccountCredentials.php
index c7a7a2dd0..086417c07 100644
--- a/src/Credentials/ServiceAccountCredentials.php
+++ b/src/Credentials/ServiceAccountCredentials.php
@@ -341,7 +341,10 @@ public function getQuotaProject()
      */
     public function getUniverseDomain(): string
     {
-        return $this->universeDomain ?: self::DEFAULT_UNIVERSE_DOMAIN;
+        if (null === $this->universeDomain) {
+            return self::DEFAULT_UNIVERSE_DOMAIN;
+        }
+        return $this->universeDomain;
     }
 
     /**
diff --git a/tests/ApplicationDefaultCredentialsTest.php b/tests/ApplicationDefaultCredentialsTest.php
index f80372473..d7c2074ad 100644
--- a/tests/ApplicationDefaultCredentialsTest.php
+++ b/tests/ApplicationDefaultCredentialsTest.php
@@ -798,34 +798,10 @@ public function testUniverseDomainInKeyFile()
         $creds = ApplicationDefaultCredentials::getCredentials();
         $this->assertEquals('example-universe.com', $creds->getUniverseDomain());
 
-        // test passing in a different universe domain overrides keyfile
-        $creds3 = ApplicationDefaultCredentials::getCredentials(
-            null,
-            null,
-            null,
-            null,
-            null,
-            null,
-            'example-universe2.com'
-        );
-        $this->assertEquals('example-universe2.com', $creds3->getUniverseDomain());
-
         // Test universe domain in "authenticated_user" keyfile is not read.
         $keyFile = __DIR__ . '/fixtures2/private.json';
         putenv(ServiceAccountCredentials::ENV_VAR . '=' . $keyFile);
         $creds2 = ApplicationDefaultCredentials::getCredentials();
         $this->assertEquals(CredentialsLoader::DEFAULT_UNIVERSE_DOMAIN, $creds2->getUniverseDomain());
-
-        // test passing in a different universe domain for "authenticated_user" has no effect.
-        $creds3 = ApplicationDefaultCredentials::getCredentials(
-            null,
-            null,
-            null,
-            null,
-            null,
-            null,
-            'example-universe2.com'
-        );
-        $this->assertEquals(CredentialsLoader::DEFAULT_UNIVERSE_DOMAIN, $creds3->getUniverseDomain());
     }
 }