diff --git a/src/main/java/io/hoangtien2k3/commons/factory/ModelMapperFactory.java b/src/main/java/io/hoangtien2k3/commons/factory/ModelMapperFactory.java
index f113ca9..90613c5 100644
--- a/src/main/java/io/hoangtien2k3/commons/factory/ModelMapperFactory.java
+++ b/src/main/java/io/hoangtien2k3/commons/factory/ModelMapperFactory.java
@@ -17,7 +17,7 @@
 import org.modelmapper.ModelMapper;
 
 public class ModelMapperFactory {
-  private static ModelMapper modelMapper = new ModelMapper();
+  private static final ModelMapper modelMapper = new ModelMapper();
 
   public static ModelMapper getInstance() {
     return modelMapper;