diff --git a/tests/unit-tests/plugins/woocommerce-subscriptions/class-subscriptions-meta.php b/tests/unit-tests/plugins/woocommerce-subscriptions/class-subscriptions-meta.php
index 5c07a12cfd..3717bce7ac 100644
--- a/tests/unit-tests/plugins/woocommerce-subscriptions/class-subscriptions-meta.php
+++ b/tests/unit-tests/plugins/woocommerce-subscriptions/class-subscriptions-meta.php
@@ -16,7 +16,7 @@ class Newspack_Test_Subscriptions_Meta extends WP_UnitTestCase {
 	 * Setup for the tests.
 	 */
 	public function set_up() {
-		define( WooCommerce_Subscriptions::NEWSPACK_SUBSCRIPTIONS_EXPIRATION_FEATURE_FLAG, true );
+		define( 'NEWSPACK_SUBSCRIPTIONS_EXPIRATION', true );
 		WooCommerce_Subscriptions::init();
 	}
 
diff --git a/tests/unit-tests/plugins/woocommerce-subscriptions/class-woocommerce-subscriptions.php b/tests/unit-tests/plugins/woocommerce-subscriptions/class-woocommerce-subscriptions.php
index 13a80ff005..159c31626a 100644
--- a/tests/unit-tests/plugins/woocommerce-subscriptions/class-woocommerce-subscriptions.php
+++ b/tests/unit-tests/plugins/woocommerce-subscriptions/class-woocommerce-subscriptions.php
@@ -22,11 +22,14 @@ public function test_is_active() {
 
 	/**
 	 * Test WooCommerce_Subscriptions::is_enabled.
+	 *
+	 * @runInSeparateProcess
+	 * @preserveGlobalState disabled
 	 */
 	public function test_is_enabled() {
 		$is_active = WooCommerce_Subscriptions::is_enabled();
 		$this->assertFalse( $is_active, 'WooCommerce Subscriptions integration should be disabled when Feature Flag is not present.' );
-		define( WooCommerce_Subscriptions::NEWSPACK_SUBSCRIPTIONS_EXPIRATION_FEATURE_FLAG, true );
+		define( 'NEWSPACK_SUBSCRIPTIONS_EXPIRATION', true );
 		$is_active = WooCommerce_Subscriptions::is_enabled();
 		$this->assertTrue( $is_active, 'WooCommerce Subscriptions integration should be enabled when Feature Flag is present.' );
 	}