diff --git a/src/node.ts b/src/node.ts
index 8ff1f6cf7..326f80e22 100644
--- a/src/node.ts
+++ b/src/node.ts
@@ -139,7 +139,7 @@ export class LocalNode {
             case "newContent":
                 return this.handleNewContent(msg);
             case "wrongAssumedKnownState":
-                return this.handleWrongAssumedKnownState(msg);
+                return this.handleWrongAssumedKnownState(msg, peer);
             case "unsubscribe":
                 return this.handleUnsubscribe(msg);
         }
@@ -161,9 +161,14 @@ export class LocalNode {
     }
 
     handleWrongAssumedKnownState(
-        msg: WrongAssumedKnownStateMessage
+        msg: WrongAssumedKnownStateMessage,
+        peer: PeerState
     ): SyncMessage | undefined {
-        return undefined;
+        const multilog = this.expectMultiLogLoaded(msg.knownState.multilogID);
+
+        peer.optimisticKnownStates[msg.knownState.multilogID] = msg.knownState;
+
+        return multilog.newContentSince(msg.knownState);
     }
 
     handleUnsubscribe(msg: UnsubscribeMessage): SyncMessage | undefined {
diff --git a/src/sync.test.ts b/src/sync.test.ts
index 352a3affc..1ddf187d2 100644
--- a/src/sync.test.ts
+++ b/src/sync.test.ts
@@ -265,6 +265,95 @@ test("After subscribing, node sends new txs to peer", async () => {
     } satisfies SyncMessage);
 });
 
+test("No matter the optimistic known state, node respects invalid known state messages and resyncs", async () => {
+    const admin = newRandomAgentCredential();
+    const adminID = getAgentID(getAgent(admin));
+
+    const node = new LocalNode(admin, newRandomSessionID(adminID));
+
+    const team = node.createTeam();
+
+    const map = team.createMap();
+
+    const [inRx, inTx] = newStreamPair<SyncMessage>();
+    const [outRx, outTx] = newStreamPair<SyncMessage>();
+
+    node.addPeer({
+        id: "test",
+        incoming: inRx,
+        outgoing: outTx,
+    });
+
+    const writer = inTx.getWriter();
+
+    await writer.write({
+        type: "subscribe",
+        knownState: {
+            multilogID: map.multiLog.id,
+            header: false,
+            sessions: {
+                [node.ownSessionID]: 0,
+            },
+        },
+    });
+
+    const reader = outRx.getReader();
+
+    const _firstMessage = await reader.read();
+
+    map.edit((editable) => {
+        editable.set("hello", "world", "trusting");
+    });
+
+    map.edit((editable) => {
+        editable.set("goodbye", "world", "trusting");
+    });
+
+    const _secondMessage = await reader.read();
+    const _thirdMessage = await reader.read();
+
+    await writer.write({
+        type: "wrongAssumedKnownState",
+        knownState: {
+            multilogID: map.multiLog.id,
+            header: true,
+            sessions: {
+                [node.ownSessionID]: 1,
+            },
+        },
+    } satisfies SyncMessage);
+
+    const fourthMessage = await reader.read();
+
+    expect(fourthMessage.value).toEqual({
+        type: "newContent",
+        multilogID: map.multiLog.id,
+        header: undefined,
+        newContent: {
+            [node.ownSessionID]: {
+                after: 1,
+                newTransactions: [
+                    {
+                        privacy: "trusting",
+                        madeAt: map.multiLog.sessions[node.ownSessionID]
+                            .transactions[1].madeAt,
+                        changes: [
+                            {
+                                op: "insert",
+                                key: "goodbye",
+                                value: "world",
+                            } satisfies MapOpPayload<string, string>,
+                        ],
+                    },
+                ],
+                lastHash: map.multiLog.sessions[node.ownSessionID].lastHash!,
+                lastSignature:
+                    map.multiLog.sessions[node.ownSessionID].lastSignature!,
+            },
+        },
+    } satisfies SyncMessage);
+});
+
 function newStreamPair<T>(): [ReadableStream<T>, WritableStream<T>] {
     const queue: T[] = [];
     let resolveNextItemReady: () => void = () => {};
@@ -274,14 +363,18 @@ function newStreamPair<T>(): [ReadableStream<T>, WritableStream<T>] {
 
     const readable = new ReadableStream<T>({
         async pull(controller) {
-            if (queue.length > 0) {
-                controller.enqueue(queue.shift());
-            } else {
-                await nextItemReady;
-                nextItemReady = new Promise((resolve) => {
-                    resolveNextItemReady = resolve;
-                });
-                controller.enqueue(queue.shift());
+            while(true) {
+                if (queue.length > 0) {
+                    controller.enqueue(queue.shift());
+                    if (queue.length === 0) {
+                        nextItemReady = new Promise((resolve) => {
+                            resolveNextItemReady = resolve;
+                        });
+                    }
+                    return;
+                } else {
+                    await nextItemReady;
+                }
             }
         },
     });
@@ -289,7 +382,9 @@ function newStreamPair<T>(): [ReadableStream<T>, WritableStream<T>] {
     const writable = new WritableStream<T>({
         write(chunk) {
             queue.push(chunk);
-            resolveNextItemReady();
+            if (queue.length === 1) {
+                resolveNextItemReady();
+            }
         },
     });