diff --git a/src/clipboard.coffee b/src/clipboard.coffee
index 2412394a6..84ff9ab3b 100644
--- a/src/clipboard.coffee
+++ b/src/clipboard.coffee
@@ -31,7 +31,7 @@ class Clipboard
   # {::readWithMetadata}.
   #
   # * `text` The {String} to store.
-  # * `metadata` The additional info to associate with the text.
+  # * `metadata` (optional) The additional info to associate with the text.
   write: (text, metadata) ->
     @signatureForMetadata = @md5(text)
     @metadata = metadata