diff --git a/modules/swagger-core/src/main/java/io/swagger/v3/core/util/Json.java b/modules/swagger-core/src/main/java/io/swagger/v3/core/util/Json.java
index 84c318fd62..899c7476ed 100644
--- a/modules/swagger-core/src/main/java/io/swagger/v3/core/util/Json.java
+++ b/modules/swagger-core/src/main/java/io/swagger/v3/core/util/Json.java
@@ -6,13 +6,12 @@
 
 public class Json {
 
-    private static ObjectMapper mapper;
+    private static final class ObjectMapperHolder {
+        private static final ObjectMapper MAPPER = ObjectMapperFactory.createJson();
+    }
 
     public static ObjectMapper mapper() {
-        if (mapper == null) {
-            mapper = ObjectMapperFactory.createJson();
-        }
-        return mapper;
+        return ObjectMapperHolder.MAPPER;
     }
 
     public static ObjectWriter pretty() {