diff --git a/build.gradle b/build.gradle
index adb5ce5..b4562a2 100755
--- a/build.gradle
+++ b/build.gradle
@@ -3,7 +3,7 @@ apply plugin: 'java'
 sourceCompatibility = 1.8
 compileJava.options.encoding = 'UTF-8'
 
-version = '6.4.0.0'
+version = '6.6.0.0'
 jar {
     manifest {
         attributes 'Implementation-Title': 'Elasticsearch Jaso Analyzer Plugin',
@@ -17,10 +17,11 @@ repositories {
 
 dependencies {
     compile group: 'commons-collections', name: 'commons-collections', version: '3.2'
-    compile 'org.elasticsearch:elasticsearch:6.4.0'
+    compile 'org.elasticsearch:elasticsearch:6.6.0'
     compile group: 'org.apache.logging.log4j', name: 'log4j-api', version: '2.11.0'
     compile group: 'org.apache.logging.log4j', name: 'log4j-core', version: '2.11.0'
     testCompile group: 'junit', name: 'junit', version: '4.+'
+    compile group: 'org.slf4j', name: 'slf4j-api', version: '1.7.25'
     
 }
 
diff --git a/src/main/java/org/elasticsearch/analysis/BaseTokenizer.java b/src/main/java/org/elasticsearch/analysis/BaseTokenizer.java
index fa3bd67..356cd94 100755
--- a/src/main/java/org/elasticsearch/analysis/BaseTokenizer.java
+++ b/src/main/java/org/elasticsearch/analysis/BaseTokenizer.java
@@ -1,12 +1,12 @@
 package org.elasticsearch.analysis;
 
-import org.apache.logging.log4j.Logger;
 import org.apache.lucene.analysis.Tokenizer;
 import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
 import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;
 import org.apache.lucene.analysis.CharacterUtils;
 import org.apache.lucene.analysis.CharacterUtils.CharacterBuffer;
-import org.elasticsearch.common.logging.*;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import java.io.*;
 
@@ -36,7 +36,7 @@ public abstract class BaseTokenizer extends Tokenizer {
     protected BaseTokenizer(TokenizerOptions options) {
         this.options = options;
 
-        logger = ESLoggerFactory.getLogger(options.getName());
+        logger = LoggerFactory.getLogger(options.getName());
         termAtt = addAttribute(CharTermAttribute.class);
         offsetAtt = addAttribute(OffsetAttribute.class);
 
diff --git a/src/main/resources/plugin-descriptor.properties b/src/main/resources/plugin-descriptor.properties
index 06cb1d1..eb478a4 100644
--- a/src/main/resources/plugin-descriptor.properties
+++ b/src/main/resources/plugin-descriptor.properties
@@ -1,6 +1,6 @@
 description=Jaso Korean Text Analyzer
-version=6.4.0.0
+version=6.6.0.0
 name=jaso-analyzer
 classname=org.elasticsearch.plugin.analysis.JasoAnalysisPlugin
 java.version=1.8
-elasticsearch.version=6.4.0
\ No newline at end of file
+elasticsearch.version=6.6.0
\ No newline at end of file