diff --git tests/phpunit/includes/bootstrap.php tests/phpunit/includes/bootstrap.php
index 460d5fbeba..b774512a4e 100644
--- tests/phpunit/includes/bootstrap.php
+++ tests/phpunit/includes/bootstrap.php
@@ -66,7 +66,11 @@ $phpmailer = new MockPHPMailer( true );
 if ( ! defined( 'WP_DEFAULT_THEME' ) ) {
 	define( 'WP_DEFAULT_THEME', 'default' );
 }
-$wp_theme_directories = array( DIR_TESTDATA . '/themedir1' );
+$wp_theme_directories = array();
+
+if ( file_exists( DIR_TESTDATA . '/themedir1' ) ) {
+	$wp_theme_directories[] = DIR_TESTDATA . '/themedir1';
+}
 
 system( WP_PHP_BINARY . ' ' . escapeshellarg( dirname( __FILE__ ) . '/install.php' ) . ' ' . escapeshellarg( $config_file_path ) . ' ' . $multisite, $retval );
 if ( 0 !== $retval ) {