diff --git a/src/services/NotificationService.ts b/src/services/NotificationService.ts
index 1b49710..a59d31e 100644
--- a/src/services/NotificationService.ts
+++ b/src/services/NotificationService.ts
@@ -198,7 +198,18 @@ export class NotificationService {
    * @param stopId Stop ID of the ETA object.
    */
   public async cancelNotificationIfExists({ deviceId, shuttleId, stopId }: ScheduledNotificationData) {
+    const tupleKey = new TupleKey(shuttleId, stopId);
+    if (
+      this.deviceIdsToDeliverTo[tupleKey.toString()] === undefined
+      || !this.deviceIdsToDeliverTo[tupleKey.toString()].includes(deviceId)
+    ) {
+      return;
+    }
 
+    const index = this.deviceIdsToDeliverTo[tupleKey.toString()].findIndex(id => id === deviceId);
+    if (index !== -1) {
+      this.deviceIdsToDeliverTo[tupleKey.toString()].splice(index, 1);
+    }
   }
 
   /**