diff --git a/src/matrix/room/BaseRoom.js b/src/matrix/room/BaseRoom.js
index 1c1e3720..9e47a7d8 100644
--- a/src/matrix/room/BaseRoom.js
+++ b/src/matrix/room/BaseRoom.js
@@ -30,6 +30,7 @@ import {DecryptionSource} from "../e2ee/common.js";
 import {ensureLogItem} from "../../logging/utils";
 import {PowerLevels} from "./PowerLevels.js";
 import {RetainedObservableValue} from "../../observable/ObservableValue";
+import {NonPersistedEventEntry} from "./timeline/entries/NonPersistedEventEntry";
 
 const EVENT_ENCRYPTED_TYPE = "m.room.encrypted";
 
@@ -570,7 +571,7 @@ export class BaseRoom extends EventEmitter {
             displayName: member.content.displayname,
             avatarUrl: member.content.avatar_url
         };
-        return new EventEntry(entry, this._fragmentIdComparer);
+        return new NonPersistedEventEntry(entry, this._fragmentIdComparer);
     }
 
 
diff --git a/src/matrix/room/timeline/entries/NonPersistedEventEntry.js b/src/matrix/room/timeline/entries/NonPersistedEventEntry.js
new file mode 100644
index 00000000..f3bae9d2
--- /dev/null
+++ b/src/matrix/room/timeline/entries/NonPersistedEventEntry.js
@@ -0,0 +1,28 @@
+/*
+Copyright 2021 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import {EventEntry} from "./EventEntry.js";
+
+// EventEntry but without the two properties that are populated via SyncWriter
+export class NonPersistedEventEntry extends EventEntry {
+    get fragmentId() {
+        throw new Error("Cannot access fragmentId for non-persisted EventEntry");
+    }
+
+    get entryIndex() {
+        throw new Error("Cannot access entryIndex for non-persisted EventEntry");
+    }
+}