diff --git a/CHANGES.md b/CHANGES.md
index 7f9aae698e2..5f5c35aaf0f 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -33,8 +33,8 @@ may not be compatible.
     a `TotalSupplyNotTrackableException` but returns a zero amount of
     corresponding `FungibleAssetValue`.  [[#3780]]
  -  (Libplanet.Action) Changed the precednce for the types of `Exception`s
-    that may be thrown by `IWorldState.MintAsset()` and
-    `IWorldState.BurnAsset()`.
+    that may be thrown by `IWorld.MintAsset()` and
+    `IWorld.BurnAsset()`.
 
 ### Backward-incompatible network protocol changes
 
diff --git a/Libplanet.Action/State/IStateStoreExtensions.cs b/Libplanet.Action/State/IStateStoreExtensions.cs
index 5b2ff4658f2..c880279cb22 100644
--- a/Libplanet.Action/State/IStateStoreExtensions.cs
+++ b/Libplanet.Action/State/IStateStoreExtensions.cs
@@ -1,12 +1,10 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Numerics;
 using System.Security.Cryptography;
 using System.Text;
 using Bencodex.Types;
 using Libplanet.Common;
-using Libplanet.Crypto;
 using Libplanet.Store;
 using Libplanet.Store.Trie;
 using Libplanet.Types.Blocks;
@@ -157,7 +155,7 @@ internal static IWorld MigrateWorld(
                 }
             }
 
-            // Migrate up to BlockMetadata.ValidatorSetAccountProtocolVersion
+            // Migrate up to BlockMetadata.CurrencyAccountProtocolVersion
             // if conditions are met.
             if (targetVersion >= BlockMetadata.CurrencyAccountProtocolVersion &&
                 world.Version < BlockMetadata.CurrencyAccountProtocolVersion)