diff --git a/spec/unit/event-timeline-set.spec.ts b/spec/unit/event-timeline-set.spec.ts
index 6f03e774553..83844fe8670 100644
--- a/spec/unit/event-timeline-set.spec.ts
+++ b/spec/unit/event-timeline-set.spec.ts
@@ -284,19 +284,27 @@ describe("EventTimelineSet", () => {
                     sender,
                 });
 
-                jest.spyOn(client, "paginateEventTimeline").mockImplementation(async () => {
-                    thread.timelineSet.getLiveTimeline().addEvent(threadReply, { toStartOfTimeline: true });
-                    return true;
-                });
-                jest.spyOn(client, "relations").mockResolvedValue({
-                    events: [],
-                });
-
-                const thread = room.createThread(root.getId()!, root, [threadReply, editToThreadReply], false);
-                thread.once(RoomEvent.TimelineReset, () => {
-                    const lastEvent = thread.timeline.at(-1)!;
-                    expect(lastEvent.getContent().body).toBe(" * edit");
-                });
+                // Mock methods that call out to HTTP endpoints
+                jest.spyOn(client, "paginateEventTimeline").mockResolvedValue(true);
+                jest.spyOn(client, "relations").mockResolvedValue({ events: [] });
+                jest.spyOn(client, "fetchRoomEvent").mockResolvedValue({});
+
+                // Create a thread and wait for it to be initialised
+                const thread = room.createThread(root.getId()!, root, [], false);
+                await new Promise<void>((res) => thread.once(RoomEvent.TimelineReset, () => res()));
+
+                // When a message and an edit are added to the thread
+                await thread.addEvent(threadReply, false);
+                await thread.addEvent(editToThreadReply, false);
+
+                // Then both events end up in the timeline
+                const lastEvent = thread.timeline.at(-1)!;
+                const secondLastEvent = thread.timeline.at(-2)!;
+                expect(lastEvent).toBe(editToThreadReply);
+                expect(secondLastEvent).toBe(threadReply);
+
+                // And the first message has been edited
+                expect(secondLastEvent.getContent().body).toEqual("edit");
             });
         });