diff --git a/src/matrix/Session.js b/src/matrix/Session.js
index daa9ecb1..b239000d 100644
--- a/src/matrix/Session.js
+++ b/src/matrix/Session.js
@@ -393,8 +393,8 @@ export class Session {
             changes.e2eeAccountChanges = this._e2eeAccount.writeSync(deviceOneTimeKeysCount, txn, log);
         }
     
-        const deviceLists = syncResponse.device_lists;
-        if (this._deviceTracker && Array.isArray(deviceLists.changed) && deviceLists.changed.length) {
+        const deviceLists = syncResponse?.device_lists;
+        if (this._deviceTracker && Array.isArray(deviceLists?.changed) && deviceLists.changed.length) {
             await log.wrap("deviceLists", log => this._deviceTracker.writeDeviceChanges(deviceLists.changed, txn, log));
         }