diff --git a/src/repository.ts b/src/repository.ts
index 51114b4..657c43b 100644
--- a/src/repository.ts
+++ b/src/repository.ts
@@ -41,8 +41,8 @@ export interface IEta {
 }
 
 export interface IOrderedStop {
-  nextStopId: string;
-  previousStopId: string;
+  nextStopId?: string;
+  previousStopId?: string;
   routeId: string;
   stopId: string;
 }