diff --git a/src/main/java/com/amazon/opendistroforelasticsearch/knn/index/codec/KNN84Codec/KNN84Codec.java b/src/main/java/com/amazon/opendistroforelasticsearch/knn/index/codec/KNN84Codec/KNN84Codec.java
index 30c3d1c5..9c3ae88c 100644
--- a/src/main/java/com/amazon/opendistroforelasticsearch/knn/index/codec/KNN84Codec/KNN84Codec.java
+++ b/src/main/java/com/amazon/opendistroforelasticsearch/knn/index/codec/KNN84Codec/KNN84Codec.java
@@ -44,6 +44,7 @@ public final class KNN84Codec extends Codec {
     private final DocValuesFormat perFieldDocValuesFormat;
     private final CompoundFormat compoundFormat;
     private Codec lucene84Codec;
+    private PostingsFormat postingsFormat = null;
 
     public static final String KNN_84 = "KNN84Codec";
     public static final String LUCENE_84 = "Lucene84"; // Lucene Codec to be used
@@ -82,9 +83,16 @@ public DocValuesFormat docValuesFormat() {
      * approach of manually overriding.
      */
 
+    public void setPostingsFormat(PostingsFormat postingsFormat) {
+        this.postingsFormat = postingsFormat;
+    }
+
     @Override
     public PostingsFormat postingsFormat() {
-        return getDelegatee().postingsFormat();
+        if (this.postingsFormat == null) {
+            return getDelegatee().postingsFormat();
+        }
+        return this.postingsFormat;
     }
 
     @Override
diff --git a/src/main/java/com/amazon/opendistroforelasticsearch/knn/plugin/KNNCodecService.java b/src/main/java/com/amazon/opendistroforelasticsearch/knn/plugin/KNNCodecService.java
index f3119247..df157ab8 100644
--- a/src/main/java/com/amazon/opendistroforelasticsearch/knn/plugin/KNNCodecService.java
+++ b/src/main/java/com/amazon/opendistroforelasticsearch/knn/plugin/KNNCodecService.java
@@ -16,7 +16,9 @@
 
 package com.amazon.opendistroforelasticsearch.knn.plugin;
 
+import com.amazon.opendistroforelasticsearch.knn.index.codec.KNN84Codec.KNN84Codec;
 import org.apache.lucene.codecs.Codec;
+import org.apache.lucene.codecs.PostingsFormat;
 import org.elasticsearch.index.codec.CodecService;
 
 import static com.amazon.opendistroforelasticsearch.knn.index.codec.KNN84Codec.KNN84Codec.KNN_84;
@@ -35,7 +37,7 @@ class KNNCodecService extends CodecService {
      * return the KNN Codec
      *
      * @param name dummy name
-     * @return KNN80Codec
+     * @return KNN84Codec
      */
     @Override
     public Codec codec(String name) {
@@ -45,4 +47,9 @@ public Codec codec(String name) {
         }
         return codec;
     }
+
+    public void setPostingsFormat(PostingsFormat postingsFormat) {
+        ((KNN84Codec)codec("")).setPostingsFormat(postingsFormat);
+    }
+
 }
diff --git a/src/main/java/com/amazon/opendistroforelasticsearch/knn/plugin/KNNEngineFactory.java b/src/main/java/com/amazon/opendistroforelasticsearch/knn/plugin/KNNEngineFactory.java
index c70be1b9..879a1dcc 100644
--- a/src/main/java/com/amazon/opendistroforelasticsearch/knn/plugin/KNNEngineFactory.java
+++ b/src/main/java/com/amazon/opendistroforelasticsearch/knn/plugin/KNNEngineFactory.java
@@ -16,7 +16,6 @@
 
 package com.amazon.opendistroforelasticsearch.knn.plugin;
 
-import org.elasticsearch.index.codec.CodecService;
 import org.elasticsearch.index.engine.Engine;
 import org.elasticsearch.index.engine.EngineConfig;
 import org.elasticsearch.index.engine.EngineFactory;
@@ -27,10 +26,11 @@
  */
 class KNNEngineFactory implements EngineFactory {
 
-    private static CodecService codecService = new KNNCodecService();
+    private static KNNCodecService codecService = new KNNCodecService();
 
     @Override
     public Engine newReadWriteEngine(EngineConfig config) {
+        codecService.setPostingsFormat(config.getCodec().postingsFormat());
         EngineConfig engineConfig = new EngineConfig(config.getShardId(), config.getAllocationId(),
                 config.getThreadPool(), config.getIndexSettings(), config.getWarmer(), config.getStore(),
                 config.getMergePolicy(), config.getAnalyzer(), config.getSimilarity(), codecService,