$siteurl = get_option( 'siteurl' );
$upload_path = get_option( 'upload_path' );
$upload_path = trim($upload_path);
- $main_override = defined( 'MULTISITE' ) && is_main_site();
+ $main_override = is_multisite() && defined( 'MULTISITE' ) && is_main_site();
if ( empty($upload_path) ) {
$dir = WP_CONTENT_DIR . '/uploads';
} else {