diff --git a/core/common/src/main/java/org/onosproject/codec/impl/CriterionCodec.java b/core/common/src/main/java/org/onosproject/codec/impl/CriterionCodec.java
index 24b749c..93cfe5d 100644
--- a/core/common/src/main/java/org/onosproject/codec/impl/CriterionCodec.java
+++ b/core/common/src/main/java/org/onosproject/codec/impl/CriterionCodec.java
@@ -82,6 +82,7 @@
     static final String PI_MATCH_MASK = "mask";
     static final String PI_MATCH_HIGH_VALUE = "highValue";
     static final String PI_MATCH_LOW_VALUE = "lowValue";
+    static final String EXTENSION = "extension";
 
     @Override
     public ObjectNode encode(Criterion criterion, CodecContext context) {