diff --git a/src/main/scala/org/scalajs/dom/Html.scala b/src/main/scala/org/scalajs/dom/Html.scala
index 854a5d522..d47274fdf 100644
--- a/src/main/scala/org/scalajs/dom/Html.scala
+++ b/src/main/scala/org/scalajs/dom/Html.scala
@@ -58,7 +58,7 @@ class HTMLDocument extends Document {
    *
    * MDN
    */
-  def cookie: String = ???
+  var cookie: String = ???
 
   /**
    * The Document.dir property is a DOMString representing the directionality of the