diff --git src/wp-admin/my-sites.php src/wp-admin/my-sites.php
index 54f5bc4..8f94190 100644
--- src/wp-admin/my-sites.php
+++ src/wp-admin/my-sites.php
@@ -23,7 +23,8 @@ $updated = false;
 if ( 'updateblogsettings' == $action && isset( $_POST['primary_blog'] ) ) {
 	check_admin_referer( 'update-my-sites' );
 
-	$blog = get_blog_details( (int) $_POST['primary_blog'] );
+	$site_id = (int) $_POST['primary_blog'];
+	$blog = get_site( $site_id );
 	if ( $blog && isset( $blog->domain ) ) {
 		update_user_option( $current_user->ID, 'primary_blog', (int) $_POST['primary_blog'], true );
 		$updated = true;