diff --git a/wp-includes/ms-functions.php b/wp-includes/ms-functions.php
index b0696d6614..65f629cb10 100644
--- a/wp-includes/ms-functions.php
+++ b/wp-includes/ms-functions.php
@@ -843,7 +843,7 @@ function wpmu_create_user( $user_name, $password, $email) {
 }
 
 function wpmu_create_blog($domain, $path, $title, $user_id, $meta = '', $site_id = 1) {
-	$domain = preg_replace( '/\s+/', '', sanitize_user( $domain, true ) );
+	$domain = preg_replace( '/\s+/', '', sanitize_key( $domain ) );
 
 	if ( is_subdomain_install() )
 		$domain = str_replace( '@', '', $domain );
diff --git a/wp-includes/taxonomy.php b/wp-includes/taxonomy.php
index c4f30b9131..6ded1b385f 100644
--- a/wp-includes/taxonomy.php
+++ b/wp-includes/taxonomy.php
@@ -352,7 +352,7 @@ function register_taxonomy( $taxonomy, $object_type, $args = array() ) {
 	unset( $args['capabilities'] );
 
 	$args['name'] = $taxonomy;
-	$args['object_type'] = (array) $object_type;
+	$args['object_type'] = is_array($object_type) ? array_map('sanitize_key', $object_type) : (array) sanitize_key($object_type);
 
 	$args['labels'] = get_taxonomy_labels( (object) $args );
 	$args['label'] = $args['labels']->name;