diff --git a/src/main/java/org/ntlab/citrusserver/repositories/ScheduleManager.java b/src/main/java/org/ntlab/citrusserver/repositories/ScheduleManager.java
index 9f19375..760568e 100644
--- a/src/main/java/org/ntlab/citrusserver/repositories/ScheduleManager.java
+++ b/src/main/java/org/ntlab/citrusserver/repositories/ScheduleManager.java
@@ -46,7 +46,9 @@
         return schedules.get(accountId).get(year).get(month).get(day);
     }
 
-    public Schedule addSchedule(String accountId, int year, int month, int day, String title, String startTime, String endTime, int bookId){
+    public Schedule addSchedule(String accountId, int year, int month, int day, String title, String startTime, String endTime, Integer bookId){
+        if(bookId == null)bookId = 0;
+
         if(!schedules.containsKey(accountId)){
             schedules.put(accountId, new HashMap<>());
         }