diff --git a/index.d.ts b/index.d.ts
index 2627cc7514..b35298e2bf 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -3058,10 +3058,7 @@ declare module 'mongoose' {
 
     export interface Group {
       /** [`$group` reference](https://docs.mongodb.com/manual/reference/operator/aggregation/group) */
-      $group: {
-        _id: any
-        [key: string]: { [op in AccumulatorOperator]?: any }
-      }
+      $group: { _id: any } | { _id: any; [key: string]: { [op in AccumulatorOperator]?: any } }
     }
 
     export interface IndexStats {