diff --git a/doc/api/fs.markdown b/doc/api/fs.markdown
index 613c45efd3a..7df7ee11583 100644
--- a/doc/api/fs.markdown
+++ b/doc/api/fs.markdown
@@ -361,7 +361,8 @@ returns a buffer.
 ### fs.writeFile(filename, data, encoding='utf8', [callback])
 
 Asynchronously writes data to a file, replacing the file if it already exists.
-`data` can be a string or a buffer.
+`data` can be a string or a buffer. The `encoding` argument is ignored if
+`data` is a buffer.
 
 Example: