diff --git a/src/Unread.ts b/src/Unread.ts
index 03a816c680..520d6c97f9 100644
--- a/src/Unread.ts
+++ b/src/Unread.ts
@@ -159,15 +159,13 @@ function makeHasReceipt(
         // If we found an event matching our receipt, then it's easy: this event
         // has a receipt if its ID is the same as the one in the receipt.
         return (ev) => ev.getId() == readUpToId;
-    } else {
-        // If we didn't, we have to guess by saying if this event is before the
-        // receipt's ts, then it we pretend it has a receipt.
-        const receipt = roomOrThread.getReadReceiptForUserId(myUserId);
-        if (receipt) {
-            const receiptTimestamp = receipt.data.ts;
-            return (ev) => ev.getTs() < receiptTimestamp;
-        } else {
-            return (_ev) => false;
-        }
     }
+
+    // If we didn't, we have to guess by saying if this event is before the
+    // receipt's ts, then it we pretend it has a receipt.
+    const receiptTs = roomOrThread.getReadReceiptForUserId(myUserId)?.data.ts ?? 0;
+    const unthreadedReceiptTs = roomOrThread.getLastUnthreadedReceiptFor(myUserId)?.ts ?? 0;
+    // We pick the more recent of the two receipts as the latest
+    const receiptTimestamp = Math.max(receiptTs, unthreadedReceiptTs);
+    return (ev) => ev.getTs() < receiptTimestamp;
 }
diff --git a/test/Unread-test.ts b/test/Unread-test.ts
index ca67257357..300acfa54b 100644
--- a/test/Unread-test.ts
+++ b/test/Unread-test.ts
@@ -22,7 +22,11 @@ import { logger } from "matrix-js-sdk/src/logger";
 import { haveRendererForEvent } from "../src/events/EventTileFactory";
 import { makeBeaconEvent, mkEvent, stubClient } from "./test-utils";
 import { mkThread } from "./test-utils/threads";
-import { doesRoomHaveUnreadMessages, eventTriggersUnreadCount } from "../src/Unread";
+import {
+    doesRoomHaveUnreadMessages,
+    doesRoomOrThreadHaveUnreadMessages,
+    eventTriggersUnreadCount,
+} from "../src/Unread";
 import { MatrixClientPeg } from "../src/MatrixClientPeg";
 
 jest.mock("../src/events/EventTileFactory", () => ({
@@ -122,7 +126,7 @@ describe("Unread", () => {
         let room: Room;
         let event: MatrixEvent;
         const roomId = "!abc:server.org";
-        const myId = client.getUserId()!;
+        const myId = client.getSafeUserId();
 
         beforeAll(() => {
             client.supportsThreads = () => true;
@@ -429,4 +433,73 @@ describe("Unread", () => {
             );
         });
     });
+
+    describe("doesRoomOrThreadHaveUnreadMessages()", () => {
+        let room: Room;
+        let event: MatrixEvent;
+        const roomId = "!abc:server.org";
+        const myId = client.getSafeUserId();
+
+        beforeAll(() => {
+            client.supportsThreads = () => true;
+        });
+
+        beforeEach(() => {
+            room = new Room(roomId, client, myId);
+            jest.spyOn(logger, "warn");
+            event = mkEvent({
+                event: true,
+                type: "m.room.message",
+                user: aliceId,
+                room: roomId,
+                content: {},
+            });
+            room.addLiveEvents([event]);
+
+            // Don't care about the code path of hidden events.
+            mocked(haveRendererForEvent).mockClear().mockReturnValue(true);
+        });
+
+        it("should consider unthreaded read receipts for main timeline", () => {
+            // Send unthreaded receipt into room pointing at the latest event
+            room.addReceipt(
+                new MatrixEvent({
+                    type: "m.receipt",
+                    room_id: "!foo:bar",
+                    content: {
+                        [event.getId()!]: {
+                            [ReceiptType.Read]: {
+                                [myId]: { ts: 1 },
+                            },
+                        },
+                    },
+                }),
+            );
+
+            expect(doesRoomOrThreadHaveUnreadMessages(room)).toBe(false);
+        });
+
+        it("should consider unthreaded read receipts for thread timelines", () => {
+            // Provide an unthreaded read receipt with ts greater than the latest thread event
+            const receipt = new MatrixEvent({
+                type: "m.receipt",
+                room_id: "!foo:bar",
+                content: {
+                    [event.getId()!]: {
+                        [ReceiptType.Read]: {
+                            [myId]: { ts: 10000000000 },
+                        },
+                    },
+                },
+            });
+            room.addReceipt(receipt);
+
+            const { thread } = mkThread({ room, client, authorId: myId, participantUserIds: [aliceId] });
+
+            expect(thread.replyToEvent!.getTs()).toBeLessThan(
+                receipt.getContent()[event.getId()!][ReceiptType.Read][myId].ts,
+            );
+            expect(doesRoomOrThreadHaveUnreadMessages(thread)).toBe(false);
+        });
+    });
 });