diff --git a/opensearch/src/test/java/org/opensearch/sql/opensearch/client/OpenSearchRestClientTest.java b/opensearch/src/test/java/org/opensearch/sql/opensearch/client/OpenSearchRestClientTest.java
index b521c6605c..cceb6de995 100644
--- a/opensearch/src/test/java/org/opensearch/sql/opensearch/client/OpenSearchRestClientTest.java
+++ b/opensearch/src/test/java/org/opensearch/sql/opensearch/client/OpenSearchRestClientTest.java
@@ -19,6 +19,7 @@
 import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
+import static org.opensearch.core.xcontent.MediaTypeParserRegistry.setDefaultMediaType;
 import static org.opensearch.sql.opensearch.client.OpenSearchClient.META_CLUSTER_NAME;
 import static org.opensearch.sql.opensearch.data.type.OpenSearchDataType.MappingType;
 
@@ -34,6 +35,7 @@
 import lombok.SneakyThrows;
 import org.apache.commons.lang3.reflect.FieldUtils;
 import org.apache.lucene.search.TotalHits;
+import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.DisplayNameGeneration;
 import org.junit.jupiter.api.DisplayNameGenerator;
@@ -101,6 +103,11 @@ void setUp() {
     client = new OpenSearchRestClient(restClient);
   }
 
+  @BeforeAll
+  static void setUpJSON() {
+    setDefaultMediaType(XContentType.JSON);
+  }
+
   @Test
   void is_index_exist() throws IOException {
     when(restClient.indices()
@@ -142,7 +149,6 @@ void create_index() throws IOException {
   @Test
   void create_index_with_IOException() throws IOException {
     when(restClient.indices().create(any(), any())).thenThrow(IOException.class);
-
     assertThrows(IllegalStateException.class,
         () -> client.createIndex("test", ImmutableMap.of()));
   }