diff --git a/src/main/java/net/onrc/onos/core/packet/DHCP.java b/src/main/java/net/onrc/onos/core/packet/DHCP.java
index ee3052b..e414802 100644
--- a/src/main/java/net/onrc/onos/core/packet/DHCP.java
+++ b/src/main/java/net/onrc/onos/core/packet/DHCP.java
@@ -53,11 +53,11 @@
      * ------------------------------------------
      */
     // Header + magic without options
-    public static int MIN_HEADER_LENGTH = 240;
-    public static byte OPCODE_REQUEST = 0x1;
-    public static byte OPCODE_REPLY = 0x2;
+    public static final int MIN_HEADER_LENGTH = 240;
+    public static final byte OPCODE_REQUEST = 0x1;
+    public static final byte OPCODE_REPLY = 0x2;
 
-    public static byte HWTYPE_ETHERNET = 0x1;
+    public static final byte HWTYPE_ETHERNET = 0x1;
 
     public enum DHCPOptionCode {
         OptionCode_SubnetMask((byte) 1),