diff --git a/activitystreams/activity.go b/activitystreams/activity.go
index aae78f0..46b3b48 100644
--- a/activitystreams/activity.go
+++ b/activitystreams/activity.go
@@ -20,6 +20,9 @@ type Activity struct {
 func NewCreateActivity(o *Object) *Activity {
 	a := Activity{
 		BaseObject: BaseObject{
+			Context: []string{
+				"https://www.w3.org/ns/activitystreams",
+			},
 			ID:   o.ID + "/activity",
 			Type: "Create",
 		},