1 files changed, 1 insertions, 1 deletions
diff --git a/chapter02/src/main/java/com/seaofnodes/simple/node/ConstantNode.java b/chapter02/src/main/java/com/seaofnodes/simple/node/ConstantNode.java
index e4d7f412..671de049 100644
--- a/chapter02/src/main/java/com/seaofnodes/simple/node/ConstantNode.java
+++ b/chapter02/src/main/java/com/seaofnodes/simple/node/ConstantNode.java
@@ -16,7 +16,7 @@ import com.seaofnodes.simple.type.Type;
  * The Constant's value is the value stored in it.
  */
 public class ConstantNode extends Node {
-    Type _con;
+    final Type _con;
     public ConstantNode( Type type ) {
         super(Parser.START);
         _con = type;