diff --git a/pom.xml b/pom.xml
index 13b0cd76d..7f97011a3 100644
--- a/pom.xml
+++ b/pom.xml
@@ -6,7 +6,7 @@
 
     <groupId>com.baidu.hugegraph</groupId>
     <artifactId>hugegraph-common</artifactId>
-    <version>1.6.5</version>
+    <version>1.6.6</version>
 
     <name>hugegraph-common</name>
     <url>https://github.com/hugegraph/hugegraph-common</url>
@@ -212,7 +212,7 @@
                         <manifestEntries>
                             <!-- Must be on one line, otherwise the automatic
                                  upgrade script cannot replace the version number -->
-                            <Implementation-Version>1.6.5.0</Implementation-Version>
+                            <Implementation-Version>1.6.6.0</Implementation-Version>
                         </manifestEntries>
                     </archive>
                 </configuration>
diff --git a/src/main/java/com/baidu/hugegraph/rest/RestClient.java b/src/main/java/com/baidu/hugegraph/rest/RestClient.java
index 63871e021..cb66395f1 100644
--- a/src/main/java/com/baidu/hugegraph/rest/RestClient.java
+++ b/src/main/java/com/baidu/hugegraph/rest/RestClient.java
@@ -24,7 +24,6 @@
 import java.util.Collection;
 import java.util.Map;
 import java.util.concurrent.Callable;
-import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
 
@@ -50,6 +49,7 @@
 import org.glassfish.jersey.message.GZipEncoder;
 import org.glassfish.jersey.uri.UriComponent;
 
+import com.baidu.hugegraph.util.ExecutorUtil;
 import com.google.common.collect.ImmutableMap;
 
 public abstract class RestClient {
@@ -98,7 +98,8 @@ public RestClient(String url, ClientConfig config) {
         this.pool = (PoolingHttpClientConnectionManager)
                     config.getProperty(CONNECTION_MANAGER);
         if (this.pool != null) {
-            this.cleanExecutor = Executors.newScheduledThreadPool(1);
+            this.cleanExecutor = ExecutorUtil.newScheduledThreadPool(
+                                              "conn-clean-worker-%d");
             this.cleanExecutor.scheduleWithFixedDelay(() -> {
                 PoolStats stats = this.pool.getTotalStats();
                 int using = stats.getLeased() + stats.getPending();
diff --git a/src/main/java/com/baidu/hugegraph/rest/RestResult.java b/src/main/java/com/baidu/hugegraph/rest/RestResult.java
index 92962eacd..e4908f8b3 100644
--- a/src/main/java/com/baidu/hugegraph/rest/RestResult.java
+++ b/src/main/java/com/baidu/hugegraph/rest/RestResult.java
@@ -77,7 +77,7 @@ public <T> List<T> readList(String key, Class<T> clazz) {
             JavaType type = mapper.getTypeFactory()
                                   .constructParametrizedType(ArrayList.class,
                                                              List.class, clazz);
-            return mapper.readValue(element.toString(), type);
+            return mapper.convertValue(element, type);
         } catch (IOException e) {
             throw new SerializeException(
                       "Failed to deserialize %s", e, this.content);
diff --git a/src/main/java/com/baidu/hugegraph/util/ExecutorUtil.java b/src/main/java/com/baidu/hugegraph/util/ExecutorUtil.java
index 773ec0d8d..e30893021 100644
--- a/src/main/java/com/baidu/hugegraph/util/ExecutorUtil.java
+++ b/src/main/java/com/baidu/hugegraph/util/ExecutorUtil.java
@@ -21,16 +21,33 @@
 
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ThreadFactory;
 
 import org.apache.commons.lang3.concurrent.BasicThreadFactory;
 
 public final class ExecutorUtil {
 
+    public static ExecutorService newFixedThreadPool(String name) {
+        return newFixedThreadPool(1, name);
+    }
+
     public static ExecutorService newFixedThreadPool(int size, String name) {
         ThreadFactory factory = new BasicThreadFactory.Builder()
                                                       .namingPattern(name)
                                                       .build();
         return Executors.newFixedThreadPool(size, factory);
     }
+
+    public static ScheduledExecutorService newScheduledThreadPool(String name) {
+        return newScheduledThreadPool(1, name);
+    }
+
+    public static ScheduledExecutorService newScheduledThreadPool(int size,
+                                                                  String name) {
+        ThreadFactory factory = new BasicThreadFactory.Builder()
+                                                      .namingPattern(name)
+                                                      .build();
+        return Executors.newScheduledThreadPool(size, factory);
+    }
 }
diff --git a/src/main/java/com/baidu/hugegraph/version/CommonVersion.java b/src/main/java/com/baidu/hugegraph/version/CommonVersion.java
index 55585ad67..da9b44c59 100644
--- a/src/main/java/com/baidu/hugegraph/version/CommonVersion.java
+++ b/src/main/java/com/baidu/hugegraph/version/CommonVersion.java
@@ -27,5 +27,5 @@ public class CommonVersion {
 
     // The second parameter of Version.of() is for all-in-one JAR
     public static final Version VERSION = Version.of(CommonVersion.class,
-                                                     "1.6.5");
+                                                     "1.6.6");
 }