diff --git a/README.md b/README.md
index 9480032..1e3a457 100644
--- a/README.md
+++ b/README.md
@@ -38,7 +38,7 @@ ncp(source, destination, function (err) {
 You can also call ncp like `ncp(source, destination, options, callback)`. 
 `options` should be a dictionary. Currently, such options are available:
 
-  * `options.filter` - a `RegExp` instance, against which each file name is
+  * `options.filter` - a `RegExp` instance or function, against which each file name is
   tested to determine whether to copy it or not, or a function taking single
   parameter: copied file name, returning `true` or `false`, determining
   whether to copy file or not.