diff --git a/src/main/java/org/ntlab/citrusserver/repositories/ScheduleManager.java b/src/main/java/org/ntlab/citrusserver/repositories/ScheduleManager.java
index 31b4055..9f19375 100644
--- a/src/main/java/org/ntlab/citrusserver/repositories/ScheduleManager.java
+++ b/src/main/java/org/ntlab/citrusserver/repositories/ScheduleManager.java
@@ -92,7 +92,8 @@
         schedules.get(accountId).get(year).get(month).get(day).get(scheduleId).setTitle(newTitle);
     }
 
-    public void setSchedulesBookId(String accountId, int year, int month, int day, int scheduleId, int newBookId){
+    public void setSchedulesBookId(String accountId, int year, int month, int day, int scheduleId, Integer newBookId){
+        if(newBookId == null)newBookId = 0;
         schedules.get(accountId).get(year).get(month).get(day).get(scheduleId).setBookId(newBookId);
     }
 }