diff --git a/src/main/java/org/ntlab/citrusserver/repositories/BookManager.java b/src/main/java/org/ntlab/citrusserver/repositories/BookManager.java
index 0b4e3eb..0d2b459 100644
--- a/src/main/java/org/ntlab/citrusserver/repositories/BookManager.java
+++ b/src/main/java/org/ntlab/citrusserver/repositories/BookManager.java
@@ -137,6 +137,9 @@
     }
 
     public void changeAccountId(String oldAccountId, String newAccountId) {
+        if(!booksMap.containsKey(oldAccountId)) {
+            return;
+        }
         for(Book book : booksMap.get(oldAccountId).values()) {
             book.setAccountId(newAccountId);
         }
diff --git a/src/main/java/org/ntlab/citrusserver/repositories/ScheduleManager.java b/src/main/java/org/ntlab/citrusserver/repositories/ScheduleManager.java
index 57f16eb..7cedc40 100644
--- a/src/main/java/org/ntlab/citrusserver/repositories/ScheduleManager.java
+++ b/src/main/java/org/ntlab/citrusserver/repositories/ScheduleManager.java
@@ -296,6 +296,9 @@
     }
 
     public void changeAccountId(String oldAccountId, String newAccountId) {
+        if(!schedules.containsKey(oldAccountId)){
+            return;
+        }
         var oldSchedules = schedules.get(oldAccountId);
         schedules.put(newAccountId, oldSchedules);
         schedules.remove(oldAccountId);
diff --git a/src/main/java/org/ntlab/citrusserver/repositories/TodoManager.java b/src/main/java/org/ntlab/citrusserver/repositories/TodoManager.java
index 6168896..0d62fab 100644
--- a/src/main/java/org/ntlab/citrusserver/repositories/TodoManager.java
+++ b/src/main/java/org/ntlab/citrusserver/repositories/TodoManager.java
@@ -391,6 +391,9 @@
     }
 
     public void changeAccountId(String oldAccountId, String newAccountId) {
+        if(todos.containsKey(oldAccountId)) {
+            return;
+        }
         var oldTodos = todos.get(oldAccountId);
         todos.put(newAccountId, oldTodos);
         todos.remove(oldAccountId);