diff --git a/src/matrix/storage/idb/stores/GroupSessionDecryptionStore.ts b/src/matrix/storage/idb/stores/GroupSessionDecryptionStore.ts
index 2b38c1fb..b6636f13 100644
--- a/src/matrix/storage/idb/stores/GroupSessionDecryptionStore.ts
+++ b/src/matrix/storage/idb/stores/GroupSessionDecryptionStore.ts
@@ -24,13 +24,14 @@ function encodeKey(roomId: string, sessionId: string, messageIndex: number | str
 interface GroupSessionDecryption {
     eventId: string;
     timestamp: number;
-    key: string;
 }
 
-export class GroupSessionDecryptionStore {
-    private _store: Store<GroupSessionDecryption>;
+type GroupSessionEntry = GroupSessionDecryption & { key: string }
 
-    constructor(store: Store<GroupSessionDecryption>) {
+export class GroupSessionDecryptionStore {
+    private _store: Store<GroupSessionEntry>;
+
+    constructor(store: Store<GroupSessionEntry>) {
         this._store = store;
     }
 
@@ -39,8 +40,8 @@ export class GroupSessionDecryptionStore {
     }
 
     set(roomId: string, sessionId: string, messageIndex: number, decryption: GroupSessionDecryption): void {
-        decryption.key = encodeKey(roomId, sessionId, messageIndex);
-        this._store.put(decryption);
+        (decryption as GroupSessionEntry).key = encodeKey(roomId, sessionId, messageIndex);
+        this._store.put(decryption as GroupSessionEntry);
     }
     
     removeAllForRoom(roomId: string): Promise<undefined> {
diff --git a/src/matrix/storage/idb/stores/OperationStore.ts b/src/matrix/storage/idb/stores/OperationStore.ts
index 080d3e66..cccd8e2d 100644
--- a/src/matrix/storage/idb/stores/OperationStore.ts
+++ b/src/matrix/storage/idb/stores/OperationStore.ts
@@ -20,15 +20,18 @@ export function encodeScopeTypeKey(scope: string, type: string): string {
     return `${scope}|${type}`;
 }
 
-interface Operation {
+interface BaseOperation {
     id: string;
-    type: string;
     scope: string;
     userIds: string[];
-    scopeTypeKey: string;
-    roomKeyMessage: RoomKeyMessage;
 }
 
+type OperationType = { type: "share_room_key"; roomKeyMessage: RoomKeyMessage; }
+
+type Operation = BaseOperation & OperationType
+
+type OperationEntry = Operation & { scopeTypeKey: string; }
+
 interface RoomKeyMessage {
     room_id: string;
     session_id: string;
@@ -38,9 +41,9 @@ interface RoomKeyMessage {
 }
 
 export class OperationStore {
-    private _store: Store<Operation>;
+    private _store: Store<OperationEntry>;
 
-    constructor(store: Store<Operation>) {
+    constructor(store: Store<OperationEntry>) {
         this._store = store;
     }
 
@@ -62,12 +65,12 @@ export class OperationStore {
     }
 
     add(operation: Operation): void {
-        operation.scopeTypeKey = encodeScopeTypeKey(operation.scope, operation.type);
-        this._store.add(operation);
+        (operation as OperationEntry).scopeTypeKey = encodeScopeTypeKey(operation.scope, operation.type);
+        this._store.add(operation as OperationEntry);
     }
 
     update(operation: Operation): void {
-        this._store.put(operation);
+        this._store.put(operation as OperationEntry);
     }
 
     remove(id: string): Promise<undefined> {