diff --git a/src/unoptimizedInMemoryRepository.ts b/src/unoptimizedInMemoryRepository.ts
index 0674a39..d550843 100644
--- a/src/unoptimizedInMemoryRepository.ts
+++ b/src/unoptimizedInMemoryRepository.ts
@@ -127,7 +127,7 @@ export class UnoptimizedInMemoryRepository implements Repository {
   }
 
   public async addOrUpdateEta(eta: IEta): Promise<void> {
-    const index = this.etas.findIndex((e) => e.id === eta.id);
+    const index = this.etas.findIndex((e) => e.stopId === eta.stopId && e.shuttleId === eta.shuttleId);
     if (index !== -1) {
       this.etas[index] = eta;
     } else {