diff --git a/wp-admin/ms-edit.php b/wp-admin/ms-edit.php
index d826e0df48..5f6af9d1c2 100644
--- a/wp-admin/ms-edit.php
+++ b/wp-admin/ms-edit.php
@@ -265,7 +265,7 @@ switch ( $_GET['action'] ) {
 			reset( $newroles );
 			foreach ( (array) $newroles as $userid => $role ) {
 				$user = new WP_User( $userid );
-				if ( ! $user )
+				if ( empty( $user->ID ) )
 					continue;
 				$user->for_blog( $id );
 				$user->set_role( $role );
diff --git a/wp-includes/capabilities.php b/wp-includes/capabilities.php
index 22974b6f49..cb762e73cb 100644
--- a/wp-includes/capabilities.php
+++ b/wp-includes/capabilities.php
@@ -1112,7 +1112,7 @@ function author_can( $post, $capability ) {
 
 	$author = new WP_User( $post->post_author );
 
-	if ( empty( $author ) )
+	if ( empty( $author->ID ) )
 		return false;
 
 	$args = array_slice( func_get_args(), 2 );
diff --git a/wp-includes/ms-functions.php b/wp-includes/ms-functions.php
index 8f2c6b800c..2b548621b0 100644
--- a/wp-includes/ms-functions.php
+++ b/wp-includes/ms-functions.php
@@ -209,7 +209,7 @@ function add_user_to_blog( $blog_id, $user_id, $role ) {
 
 	$user = new WP_User($user_id);
 
-	if ( empty($user) || !$user->ID )
+	if ( empty( $user->ID ) )
 		return new WP_Error('user_does_not_exist', __('That user does not exist.'));
 
 	if ( !get_user_meta($user_id, 'primary_blog', true) ) {
@@ -253,6 +253,9 @@ function remove_user_from_blog($user_id, $blog_id = '', $reassign = '') {
 
 	// wp_revoke_user($user_id);
 	$user = new WP_User($user_id);
+	if ( empty( $user->ID ) )
+		return new WP_Error('user_does_not_exist', __('That user does not exist.'));
+
 	$user->remove_all_caps();
 
 	$blogs = get_blogs_of_user($user_id);
@@ -1326,10 +1329,7 @@ function is_user_spammy( $username = 0 ) {
 	}
 	$u = new WP_User( $user_id );
 
-	if ( $u->spam == 1 )
-		return true;
-
-	return false;
+	return ( isset( $u->spam ) && $u->spam == 1 );
 }
 
 function update_blog_public( $old_value, $value ) {