Index: wp-includes/query.php
===================================================================
--- wp-includes/query.php	(revision 19802)
+++ wp-includes/query.php	(working copy)
@@ -3023,9 +3023,8 @@
 		if ( empty( $post_types ) || !$this->is_post_type_archive )
 			return (bool) $this->is_post_type_archive;
 
-		$post_type_object = $this->get_queried_object();
-
-		return in_array( $post_type_object->name, (array) $post_types );
+		$queried_post_types = (array) get_query_var( 'post_type' );
+		return array_intersect( (array) $post_types, $queried_post_types );
 	}
 
 	/**