diff --git a/admin-command.php b/admin-command.php
index 25eac29..b96329b 100644
--- a/admin-command.php
+++ b/admin-command.php
@@ -7,7 +7,7 @@
 /**
  * Open /wp-admin/ in a browser.
  */
-$wp_admin = function() {
+function wp_cli_admin_command() {
 	switch ( strtoupper( substr( PHP_OS, 0, 3 ) ) ) {
 		case 'DAR':
 			$exec = 'open';
@@ -19,5 +19,5 @@
 			$exec = 'xdg-open';
 	}
 	passthru( $exec . ' ' . escapeshellarg( admin_url() ) );
-};
-WP_CLI::add_command( 'admin', $wp_admin );
+}
+WP_CLI::add_command( 'admin', 'wp_cli_admin_command' );