diff --git a/src/main/java/org/ntlab/citrusserver/repositories/ScheduleManager.java b/src/main/java/org/ntlab/citrusserver/repositories/ScheduleManager.java
index 4eb354f..076a591 100644
--- a/src/main/java/org/ntlab/citrusserver/repositories/ScheduleManager.java
+++ b/src/main/java/org/ntlab/citrusserver/repositories/ScheduleManager.java
@@ -102,8 +102,9 @@
     public int setSchedulesBookId(String accountId, int year, int month, int day, int scheduleId, Integer newBookId){
         if(newBookId == null || newBookId.equals(0)){
             newBookId = 0;
-        }
-        else if(!bookManager.getBooks(accountId).containsKey(newBookId))return -1;
+        }else if (bookManager.getBooks(accountId)==null) {
+            return -1;
+        }else if(!bookManager.getBooks(accountId).containsKey(newBookId))return -1;
         schedules.get(accountId).get(year).get(month).get(day).get(scheduleId).setBookId(newBookId);
 
         return 1;