diff --git a/lib/models/room.js b/lib/models/room.js
index ad586ff3f..f3f630ac1 100644
--- a/lib/models/room.js
+++ b/lib/models/room.js
@@ -13,7 +13,11 @@ var ContentRepo = require("../content-repo");
 function synthesizeReceipt(userId, event, receiptType) {
     // This is really ugly because JS has no way to express an object literal
     // where the name of a key comes from an expression
-    var fakeReceipt = {content: {}};
+    var fakeReceipt = {
+        content: {},
+        type: "m.receipt",
+        room_id: event.getRoomId()
+    };
     fakeReceipt.content[event.getId()] = {};
     fakeReceipt.content[event.getId()][receiptType] = {};
     fakeReceipt.content[event.getId()][receiptType][userId] = {