diff --git a/lib/Autocomplete.js b/lib/Autocomplete.js
index daceb0ed..7094e976 100644
--- a/lib/Autocomplete.js
+++ b/lib/Autocomplete.js
@@ -103,7 +103,7 @@ let Autocomplete = React.createClass({
   },
 
   keyDownHandlers: {
-    ArrowDown () {
+    ArrowDown (event) {
       event.preventDefault()
       var { highlightedIndex } = this.state
       var index = (