Ticket #33804: 33804_4.diff

src/wp-admin/network/site-new.php

@@ -90 +90 @@
         $user_id = email_exists($email);
         if ( !$user_id ) { // Create a new user with a random password
                 $password = wp_generate_password( 12, false );
+                $user_id = username_exists($domain);
+                if ( $user_id )
+                        wp_die( __( 'This username is already registered.' ) );
                 $user_id = wpmu_create_user( $domain, $password, $email );
                 if ( false === $user_id )
                         wp_die( __( 'There was an error creating the user.' ) );