diff --git a/src/matrix/Session.js b/src/matrix/Session.js
index 7a7dea52..b477c3d9 100644
--- a/src/matrix/Session.js
+++ b/src/matrix/Session.js
@@ -24,7 +24,7 @@ export class Session {
     constructor({storage, hsApi, sessionInfo}) {
         this._storage = storage;
         this._hsApi = hsApi;
-        this._session = null;
+        this._syncInfo = null;
         this._sessionInfo = sessionInfo;
         this._rooms = new ObservableMap();
         this._sendScheduler = new SendScheduler({hsApi, backoff: new RateLimitingBackoff()});
@@ -42,11 +42,7 @@ export class Session {
             this._storage.storeNames.pendingEvents,
         ]);
         // restore session object
-        this._session = await txn.session.get();
-        if (!this._session) {
-            this._session = {};
-            return;
-        }
+        this._syncInfo = await txn.session.get("sync");
         const pendingEventsByRoomId = await this._getPendingEventsByRoom(txn);
         // load rooms
         const rooms = await txn.roomSummary.getAll();
@@ -70,11 +66,9 @@ export class Session {
             const txn = await this._storage.readWriteTxn([
                 this._storage.storeNames.session
             ]);
-            const newSessionData = Object.assign({}, this._session, {serverVersions: lastVersionResponse});
-            txn.session.set(newSessionData);
+            txn.session.set("serverVersions", lastVersionResponse);
             // TODO: what can we do if this throws?
             await txn.complete();
-            this._session = newSessionData;
         }
 
         this._sendScheduler.start();
@@ -115,27 +109,27 @@ export class Session {
     }
 
     writeSync(syncToken, syncFilterId, accountData, txn) {
-        if (syncToken !== this._session.syncToken) {
-            // don't modify this._session because transaction might still fail
-            const newSessionData = Object.assign({}, this._session, {syncToken, syncFilterId});
-            txn.session.set(newSessionData);
-            return newSessionData;
+        if (syncToken !== this.syncToken) {
+            const syncInfo = {token: syncToken, filterId: syncFilterId};
+            // don't modify `this` because transaction might still fail
+            txn.session.set("sync", syncInfo);
+            return syncInfo;
         }
     }
 
-    afterSync(newSessionData) {
-        if (newSessionData) {
+    afterSync(syncInfo) {
+        if (syncInfo) {
             // sync transaction succeeded, modify object state now
-            this._session = newSessionData;
+            this._syncInfo = syncInfo;
         }
     }
 
     get syncToken() {
-        return this._session.syncToken;
+        return this._syncInfo?.token;
     }
 
     get syncFilterId() {
-        return this._session.syncFilterId;
+        return this._syncInfo?.filterId;
     }
 
     get user() {
@@ -149,8 +143,8 @@ export function tests() {
             readTxn() {
                 return Promise.resolve({
                     session: {
-                        get() {
-                            return Promise.resolve(Object.assign({}, session));
+                        get(key) {
+                            return Promise.resolve(session[key]);
                         }
                     },
                     pendingEvents: {
@@ -172,22 +166,23 @@ export function tests() {
     return {
         "session data is not modified until after sync": async (assert) => {
             const session = new Session({storage: createStorageMock({
-                syncToken: "a",
-                syncFilterId: 5,
+                sync: {token: "a", filterId: 5}
             }), sessionInfo: {userId: ""}});
             await session.load();
-            let txnSetCalled = false;
+            let syncSet = false;
             const syncTxn = {
                 session: {
-                    set({syncToken, syncFilterId}) {
-                        txnSetCalled = true;
-                        assert.equal(syncToken, "b");
-                        assert.equal(syncFilterId, 6);
+                    set(key, value) {
+                        if (key === "sync") {
+                            assert.equal(value.token, "b");
+                            assert.equal(value.filterId, 6);
+                            syncSet = true;
+                        }
                     }
                 }
             };
             const newSessionData = session.writeSync("b", 6, {}, syncTxn);
-            assert(txnSetCalled);
+            assert(syncSet);
             assert.equal(session.syncToken, "a");
             assert.equal(session.syncFilterId, 5);
             session.afterSync(newSessionData);
diff --git a/src/matrix/room/RoomSummary.js b/src/matrix/room/RoomSummary.js
index 36c7d203..b3758d23 100644
--- a/src/matrix/room/RoomSummary.js
+++ b/src/matrix/room/RoomSummary.js
@@ -263,7 +263,7 @@ export function tests() {
         "membership trigger change": function(assert) {
             const summary = new RoomSummary("id");
             let written = false;
-            const changes = summary.writeSync({}, "join", {roomSummary: {set: () => { written = true; }}});
+            const changes = summary.writeSync({}, "join", false, false, {roomSummary: {set: () => { written = true; }}});
             assert(changes);
             assert(written);
             assert.equal(changes.membership, "join");
diff --git a/src/matrix/storage/idb/schema.js b/src/matrix/storage/idb/schema.js
index 21a108c8..0ab5707a 100644
--- a/src/matrix/storage/idb/schema.js
+++ b/src/matrix/storage/idb/schema.js
@@ -1,12 +1,14 @@
-import {iterateCursor} from "./utils.js";
+import {iterateCursor, reqAsPromise} from "./utils.js";
 import {RoomMember, EVENT_TYPE as MEMBER_EVENT_TYPE} from "../../room/members/RoomMember.js";
 import {RoomMemberStore} from "./stores/RoomMemberStore.js";
+import {SessionStore} from "./stores/SessionStore.js";
 
 // FUNCTIONS SHOULD ONLY BE APPENDED!!
 // the index in the array is the database version
 export const schema = [
     createInitialStores,
     createMemberStore,
+    migrateSession,
 ];
 // TODO: how to deal with git merge conflicts of this array?
 
@@ -44,3 +46,21 @@ async function createMemberStore(db, txn) {
         }
     });
 }
+
+async function migrateSession(db, txn) {
+    const session = txn.objectStore("session");
+    try {
+        const PRE_MIGRATION_KEY = 1;
+        const entry = await reqAsPromise(session.get(PRE_MIGRATION_KEY));
+        if (entry) {
+            session.delete(PRE_MIGRATION_KEY);
+            const {syncToken, syncFilterId, serverVersions} = entry.value;
+            const store = new SessionStore(session);
+            store.set("sync", {token: syncToken, filterId: syncFilterId});
+            store.set("serverVersions", serverVersions);
+        }
+    } catch (err) {
+        txn.abort();
+        console.error("could not migrate session", err.stack);
+    }
+}
diff --git a/src/matrix/storage/idb/stores/SessionStore.js b/src/matrix/storage/idb/stores/SessionStore.js
index e26de3b4..2e74b9df 100644
--- a/src/matrix/storage/idb/stores/SessionStore.js
+++ b/src/matrix/storage/idb/stores/SessionStore.js
@@ -35,14 +35,14 @@ export class SessionStore {
 		this._sessionStore = sessionStore;
 	}
 
-	async get() {
-		const session = await this._sessionStore.selectFirst(IDBKeyRange.only(1));
-		if (session) {
-			return session.value;
+	async get(key) {
+		const entry = await this._sessionStore.get(key);
+		if (entry) {
+			return entry.value;
 		}
 	}
 
-	set(session) {
-		return this._sessionStore.put({key: 1, value: session});
+	set(key, value) {
+		return this._sessionStore.put({key, value});
 	}
 }