diff --git a/jsprit-core/src/main/java/jsprit/core/problem/io/JsonConstants.java b/jsprit-core/src/main/java/jsprit/core/problem/io/JsonConstants.java
index 645a688f..7058a5e3 100644
--- a/jsprit-core/src/main/java/jsprit/core/problem/io/JsonConstants.java
+++ b/jsprit-core/src/main/java/jsprit/core/problem/io/JsonConstants.java
@@ -47,8 +47,6 @@ public class JsonConstants {
         public static final String END = "end";
     }
 
-    public static String JOB = "job";
-
     public static class Job {
 
         public static final String SIZE = "size";