diff --git a/tests/phpunit/tests/admin/wpAutomaticUpdater.php b/tests/phpunit/tests/admin/wpAutomaticUpdater.php
index 1746d9490c9db..18ea4d6febe87 100644
--- a/tests/phpunit/tests/admin/wpAutomaticUpdater.php
+++ b/tests/phpunit/tests/admin/wpAutomaticUpdater.php
@@ -609,8 +609,17 @@ public function test_is_allowed_dir_should_return_true_if_open_basedir_is_set_an
 		$abspath_grandparent = trailingslashit( dirname( $abspath_parent ) );
 
 		$open_basedir_backup = ini_get( 'open_basedir' );
+
+		/*
+		 * Windows must use a semi-colon as a separator.
+		 * For all other operating systems, a colon should be used.
+		 *
+		 * See https://www.php.net/manual/en/ini.core.php#ini.open-basedir
+		 */
+		$separator = 'WIN' === strtoupper( substr( PHP_OS, 0, 3 ) ) ? ';' : ':';
+
 		// Allow access to the directory one level above the repository.
-		ini_set( 'open_basedir', wp_normalize_path( $abspath_grandparent ) );
+		ini_set( 'open_basedir', sys_get_temp_dir() . $separator . wp_normalize_path( $abspath_grandparent ) );
 
 		// Checking an allowed directory should succeed.
 		$actual = self::$updater->is_allowed_dir( wp_normalize_path( ABSPATH ) );
@@ -644,8 +653,17 @@ public function test_is_allowed_dir_should_return_false_if_open_basedir_is_set_a
 		$abspath_grandparent = trailingslashit( dirname( $abspath_parent ) );
 
 		$open_basedir_backup = ini_get( 'open_basedir' );
+
+		/*
+		 * Windows must use a semi-colon as a separator.
+		 * For all other operating systems, a colon should be used.
+		 *
+		 * See https://www.php.net/manual/en/ini.core.php#ini.open-basedir
+		 */
+		$separator = 'WIN' === strtoupper( substr( PHP_OS, 0, 3 ) ) ? ';' : ':';
+
 		// Allow access to the directory one level above the repository.
-		ini_set( 'open_basedir', wp_normalize_path( $abspath_grandparent ) );
+		ini_set( 'open_basedir', sys_get_temp_dir() . $separator . wp_normalize_path( $abspath_grandparent ) );
 
 		// Checking a directory not within the allowed path should trigger an `open_basedir` warning.
 		$actual = self::$updater->is_allowed_dir( '/.git' );