diff --git a/src/matrix/e2ee/DeviceTracker.js b/src/matrix/e2ee/DeviceTracker.js
index 0b4c73a2..6b6f3894 100644
--- a/src/matrix/e2ee/DeviceTracker.js
+++ b/src/matrix/e2ee/DeviceTracker.js
@@ -26,8 +26,8 @@ function deviceKeysAsDeviceIdentity(deviceSection) {
     return {
         userId,
         deviceId,
-        ed25519Key: deviceSection.keys?.[`ed25519:${deviceId}`],
-        curve25519Key: deviceSection.keys?.[`curve25519:${deviceId}`],
+        ed25519Key: deviceSection.keys[`ed25519:${deviceId}`],
+        curve25519Key: deviceSection.keys[`curve25519:${deviceId}`],
         algorithms: deviceSection.algorithms,
         displayName: deviceSection.unsigned?.device_display_name,
     };
@@ -200,6 +200,11 @@ export class DeviceTracker {
                 if (deviceIdOnKeys !== deviceId) {
                     return false;
                 }
+                const ed25519Key = deviceKeys.keys?.[`ed25519:${deviceId}`];
+                const curve25519Key = deviceKeys.keys?.[`curve25519:${deviceId}`];
+                if (typeof ed25519Key !== "string" || typeof curve25519Key !== "string") {
+                    return false;
+                }
                 // don't store our own device
                 if (userId === this._ownUserId && deviceId === this._ownDeviceId) {
                     return false;