diff --git a/dd-java-agent/instrumentation/elasticsearch-rest-5/elasticsearch-rest-5.gradle b/dd-java-agent/instrumentation/elasticsearch-rest-5/elasticsearch-rest-5.gradle
index 3ad7351cdf..ac8372a78f 100644
--- a/dd-java-agent/instrumentation/elasticsearch-rest-5/elasticsearch-rest-5.gradle
+++ b/dd-java-agent/instrumentation/elasticsearch-rest-5/elasticsearch-rest-5.gradle
@@ -10,6 +10,12 @@ muzzle {
     versions = "[5.0,6.4)"
     assertInverse = true
   }
+
+  pass {
+    group = "org.elasticsearch.client"
+    module = "elasticsearch-rest-client"
+    versions = "[5.0,6.4)"
+  }
 }
 
 apply from: "${rootDir}/gradle/java.gradle"
@@ -43,11 +49,6 @@ dependencies {
   testCompile group: 'org.elasticsearch', name: 'elasticsearch', version: '5.0.0'
   testCompile group: 'org.elasticsearch.plugin', name: 'transport-netty3-client', version: '5.0.0'
 
-  /*
-   We know that 6.3.+ Doesn't work because they've reworked relevant code.
-   See https://github.com/elastic/elasticsearch/commit/0be443c5bbd4c7eb5776740d8fb7117224124cce#diff-d5bb3520f960a753d8f8a3a2686dfd6b
-   Lock on 6.2.+ to fix tests.
-   */
   latestDepTestCompile group: 'org.elasticsearch.client', name: 'elasticsearch-rest-client', version: '6.3.+'
   latestDepTestCompile group: 'org.elasticsearch', name: 'elasticsearch', version: '6.3.+'
   latestDepTestCompile group: 'org.elasticsearch.plugin', name: 'transport-netty4-client', version: '6.3.+'
diff --git a/dd-java-agent/instrumentation/elasticsearch-rest-5/src/main/java/datadog/trace/instrumentation/elasticsearch5/Elasticsearch5RestClientInstrumentation.java b/dd-java-agent/instrumentation/elasticsearch-rest-5/src/main/java/datadog/trace/instrumentation/elasticsearch5/Elasticsearch5RestClientInstrumentation.java
index 4249dd82ba..bcd364df44 100644
--- a/dd-java-agent/instrumentation/elasticsearch-rest-5/src/main/java/datadog/trace/instrumentation/elasticsearch5/Elasticsearch5RestClientInstrumentation.java
+++ b/dd-java-agent/instrumentation/elasticsearch-rest-5/src/main/java/datadog/trace/instrumentation/elasticsearch5/Elasticsearch5RestClientInstrumentation.java
@@ -58,11 +58,11 @@ public class Elasticsearch5RestClientInstrumentation extends Instrumenter.Defaul
 
     @Advice.OnMethodEnter(suppress = Throwable.class)
     public static Scope startSpan(
-        @Advice.Argument(0) String method,
-        @Advice.Argument(1) String endpoint,
+        @Advice.Argument(0) final String method,
+        @Advice.Argument(1) final String endpoint,
         @Advice.Argument(value = 5, readOnly = false) ResponseListener responseListener) {
 
-      Scope scope =
+      final Scope scope =
           GlobalTracer.get()
               .buildSpan("elasticsearch.rest.query")
               .withTag(DDTags.SERVICE_NAME, "elasticsearch")
@@ -78,9 +78,10 @@ public class Elasticsearch5RestClientInstrumentation extends Instrumenter.Defaul
     }
 
     @Advice.OnMethodExit(onThrowable = Throwable.class, suppress = Throwable.class)
-    public static void stopSpan(@Advice.Enter Scope scope, @Advice.Thrown Throwable throwable) {
+    public static void stopSpan(
+        @Advice.Enter final Scope scope, @Advice.Thrown final Throwable throwable) {
       if (throwable != null) {
-        Span span = scope.span();
+        final Span span = scope.span();
         Tags.ERROR.set(span, true);
         span.log(Collections.singletonMap(ERROR_OBJECT, throwable));
         span.finish();
diff --git a/dd-java-agent/instrumentation/elasticsearch-rest-6.4/elasticsearch-rest-6.4.gradle b/dd-java-agent/instrumentation/elasticsearch-rest-6.4/elasticsearch-rest-6.4.gradle
index 98fad47e91..d3d511cea6 100644
--- a/dd-java-agent/instrumentation/elasticsearch-rest-6.4/elasticsearch-rest-6.4.gradle
+++ b/dd-java-agent/instrumentation/elasticsearch-rest-6.4/elasticsearch-rest-6.4.gradle
@@ -6,10 +6,17 @@ ext {
 muzzle {
   pass {
     group = "org.elasticsearch.client"
-    module = "rest" // elasticsearch-rest-client ?
+    module = "relasticsearch-rest-client"
     versions = "[6.4,)"
     assertInverse = true
   }
+
+  fail {
+    group = "org.elasticsearch.client"
+    module = "rest"
+    versions = "(,)"
+    assertInverse = true
+  }
 }
 
 apply from: "${rootDir}/gradle/java.gradle"
diff --git a/dd-java-agent/instrumentation/elasticsearch-rest-6.4/src/main/java/datadog/trace/instrumentation/elasticsearch6_4/Elasticsearch6RestClientInstrumentation.java b/dd-java-agent/instrumentation/elasticsearch-rest-6.4/src/main/java/datadog/trace/instrumentation/elasticsearch6_4/Elasticsearch6RestClientInstrumentation.java
index 88f23c8837..f439cf3e99 100644
--- a/dd-java-agent/instrumentation/elasticsearch-rest-6.4/src/main/java/datadog/trace/instrumentation/elasticsearch6_4/Elasticsearch6RestClientInstrumentation.java
+++ b/dd-java-agent/instrumentation/elasticsearch-rest-6.4/src/main/java/datadog/trace/instrumentation/elasticsearch6_4/Elasticsearch6RestClientInstrumentation.java
@@ -58,10 +58,10 @@ public class Elasticsearch6RestClientInstrumentation extends Instrumenter.Defaul
 
     @Advice.OnMethodEnter(suppress = Throwable.class)
     public static Scope startSpan(
-        @Advice.Argument(0) Request request,
+        @Advice.Argument(0) final Request request,
         @Advice.Argument(value = 1, readOnly = false) ResponseListener responseListener) {
 
-      Scope scope =
+      final Scope scope =
           GlobalTracer.get()
               .buildSpan("elasticsearch.rest.query")
               .withTag(DDTags.SERVICE_NAME, "elasticsearch")
@@ -77,9 +77,10 @@ public class Elasticsearch6RestClientInstrumentation extends Instrumenter.Defaul
     }
 
     @Advice.OnMethodExit(onThrowable = Throwable.class, suppress = Throwable.class)
-    public static void stopSpan(@Advice.Enter Scope scope, @Advice.Thrown Throwable throwable) {
+    public static void stopSpan(
+        @Advice.Enter final Scope scope, @Advice.Thrown final Throwable throwable) {
       if (throwable != null) {
-        Span span = scope.span();
+        final Span span = scope.span();
         Tags.ERROR.set(span, true);
         span.log(Collections.singletonMap(ERROR_OBJECT, throwable));
         span.finish();
diff --git a/dd-java-agent/instrumentation/elasticsearch-rest-6.4/src/main/java/datadog/trace/instrumentation/elasticsearch6_4/RestResponseListener.java b/dd-java-agent/instrumentation/elasticsearch-rest-6.4/src/main/java/datadog/trace/instrumentation/elasticsearch6_4/RestResponseListener.java
index b9842e9985..6cc0a1b9bf 100644
--- a/dd-java-agent/instrumentation/elasticsearch-rest-6.4/src/main/java/datadog/trace/instrumentation/elasticsearch6_4/RestResponseListener.java
+++ b/dd-java-agent/instrumentation/elasticsearch-rest-6.4/src/main/java/datadog/trace/instrumentation/elasticsearch6_4/RestResponseListener.java
@@ -13,13 +13,13 @@ public class RestResponseListener implements ResponseListener {
   private final ResponseListener listener;
   private final Span span;
 
-  public RestResponseListener(ResponseListener listener, Span span) {
+  public RestResponseListener(final ResponseListener listener, final Span span) {
     this.listener = listener;
     this.span = span;
   }
 
   @Override
-  public void onSuccess(Response response) {
+  public void onSuccess(final Response response) {
     if (response.getHost() != null) {
       Tags.PEER_HOSTNAME.set(span, response.getHost().getHostName());
       Tags.PEER_PORT.set(span, response.getHost().getPort());
@@ -33,7 +33,7 @@ public class RestResponseListener implements ResponseListener {
   }
 
   @Override
-  public void onFailure(Exception e) {
+  public void onFailure(final Exception e) {
     span.log(Collections.singletonMap(ERROR_OBJECT, e));
 
     try {