diff --git a/spec/unit/event-timeline.spec.js b/spec/unit/event-timeline.spec.js
index f1a8f0109..8cb2f2e48 100644
--- a/spec/unit/event-timeline.spec.js
+++ b/spec/unit/event-timeline.spec.js
@@ -16,8 +16,11 @@ describe("EventTimeline", function() {
 
     beforeEach(function() {
         utils.beforeEach(this);
-        // XXX: this is a horrid hack; should use sinon or something instead
+
+        // XXX: this is a horrid hack; should use sinon or something instead to mock
         var timelineSet = { room: { roomId: roomId }};
+        timelineSet.room.getUnfilteredTimelineSet = function() { return timelineSet; };
+
         timeline = new EventTimeline(timelineSet);
     });
 
diff --git a/spec/unit/timeline-window.spec.js b/spec/unit/timeline-window.spec.js
index f0f101ede..d04f6b585 100644
--- a/spec/unit/timeline-window.spec.js
+++ b/spec/unit/timeline-window.spec.js
@@ -20,6 +20,8 @@ function createTimeline(numEvents, baseIndex) {
 
     // XXX: this is a horrid hack
     var timelineSet = { room: { roomId: ROOM_ID }};
+    timelineSet.room.getUnfilteredTimelineSet = function() { return timelineSet; };
+
     var timeline = new EventTimeline(timelineSet);
 
     // add the events after the baseIndex first