diff --git a/opensearch-observability/build.gradle b/opensearch-observability/build.gradle
index 276ac2880..50f629e55 100644
--- a/opensearch-observability/build.gradle
+++ b/opensearch-observability/build.gradle
@@ -13,7 +13,7 @@ buildscript {
         // 1.0.0 -> 1.0.0.0, and 1.0.0-SNAPSHOT -> 1.0.0.0-SNAPSHOT
         opensearch_build = opensearch_version.replaceAll(/(\.\d)([^\d]*)$/, '$1.0$2')
         common_utils_version = System.getProperty("common_utils.version", opensearch_build)
-        kotlin_version = System.getProperty("kotlin.version", "1.6.21")
+        kotlin_version = System.getProperty("kotlin.version", "1.6.0")
     }
 
     repositories {
diff --git a/opensearch-observability/src/test/kotlin/org/opensearch/observability/PluginRestTestCase.kt b/opensearch-observability/src/test/kotlin/org/opensearch/observability/PluginRestTestCase.kt
index c80e1bddd..d2ee8ce18 100644
--- a/opensearch-observability/src/test/kotlin/org/opensearch/observability/PluginRestTestCase.kt
+++ b/opensearch-observability/src/test/kotlin/org/opensearch/observability/PluginRestTestCase.kt
@@ -26,6 +26,7 @@ import org.opensearch.client.Response
 import org.opensearch.client.ResponseException
 import org.opensearch.client.RestClient
 import org.opensearch.client.RestClientBuilder
+import org.opensearch.common.io.PathUtils
 import org.opensearch.common.settings.Settings
 import org.opensearch.common.unit.TimeValue
 import org.opensearch.common.util.concurrent.ThreadContext
@@ -263,7 +264,7 @@ abstract class PluginRestTestCase : OpenSearchRestTestCase() {
                     false
                 )
                 proxy.getExecutionData(false)?.let {
-                    val path = Paths.get("$jacocoBuildPath/integTest.exec")
+                    val path = PathUtils.get("$jacocoBuildPath/integTest.exec")
                     Files.write(path, it)
                 }
             }
diff --git a/opensearch-observability/src/test/kotlin/org/opensearch/observability/bwc/TABackwardCompatibilityIT.kt b/opensearch-observability/src/test/kotlin/org/opensearch/observability/bwc/TABackwardCompatibilityIT.kt
index cc709de4a..f23ed095f 100644
--- a/opensearch-observability/src/test/kotlin/org/opensearch/observability/bwc/TABackwardCompatibilityIT.kt
+++ b/opensearch-observability/src/test/kotlin/org/opensearch/observability/bwc/TABackwardCompatibilityIT.kt
@@ -13,8 +13,8 @@ import org.opensearch.observability.PluginRestTestCase
 import org.opensearch.observability.constructNotebookRequest
 import org.opensearch.rest.RestRequest
 import org.opensearch.rest.RestStatus
-import java.util.List
-import java.util.Map
+// import kotlin.Collections.List
+// import kotlin.Collections.Map
 
 class TABackwardCompatibilityIT : PluginRestTestCase() {
 
@@ -61,14 +61,14 @@ class TABackwardCompatibilityIT : PluginRestTestCase() {
     }
 
     @Throws(Exception::class)
-    @SuppressWarnings("unchecked")
+    @SuppressWarnings("UNCHECKED_CAST")
     fun `test backwards compatibility`() {
         val uri = getUri()
         val responseMap = getAsMap(uri)["nodes"] as Map<String, Map<String, Any>>
-        for (response in responseMap.values()) {
+        for (response in responseMap.values) {
             val plugins = response["plugins"] as List<Map<String, Any>>
             val pluginNames = plugins.map { plugin -> plugin["name"] }.toSet()
-            return when (CLUSTER_TYPE) {
+            when (CLUSTER_TYPE) {
                 ClusterType.OLD -> {
                     assertTrue(pluginNames.contains("opensearch-notebooks"))
                     createNotebook()