diff --git a/examples/mongodb-crud/backend/src/models/Global.ts b/examples/mongodb-crud/backend/src/models/Global.ts
index 7804839..d86f33a 100644
--- a/examples/mongodb-crud/backend/src/models/Global.ts
+++ b/examples/mongodb-crud/backend/src/models/Global.ts
@@ -1,4 +1,4 @@
-import { Collection, Db, MongoClient } from "mongodb";
+import { Collection, Db, MongoClient, OptionalId } from "mongodb";
 import { Logger } from "tsrpc";
 import { DbPost } from "../shared/db/DbPost";
 import { BackConfig } from "./BackConfig";
@@ -14,7 +14,7 @@ export class Global {
         this.db = client.db();
     }
 
-    static collection<T extends keyof DbCollectionType>(col: T): Collection<DbCollectionType[T]> {
+    static collection<T extends keyof DbCollectionType>(col: T): Collection<OptionalId<DbCollectionType[T]>> {
         return this.db.collection(col);
     }