diff --git a/.travis.yml b/.travis.yml
index 43fa8a0d2..8df38075e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,7 +1,7 @@
 language: java
 
 jdk:
-  - oraclejdk8
+  - openjdk8
 
 install: mvn compile -Dmaven.javadoc.skip=true
 
diff --git a/pom.xml b/pom.xml
index 0bb469425..7cc353b49 100644
--- a/pom.xml
+++ b/pom.xml
@@ -6,7 +6,7 @@
 
     <groupId>com.baidu.hugegraph</groupId>
     <artifactId>hugegraph-common</artifactId>
-    <version>1.6.11</version>
+    <version>1.6.12</version>
 
     <name>hugegraph-common</name>
     <url>https://github.com/hugegraph/hugegraph-common</url>
diff --git a/src/main/java/com/baidu/hugegraph/util/Bytes.java b/src/main/java/com/baidu/hugegraph/util/Bytes.java
index 2743a38a1..b882e3fec 100644
--- a/src/main/java/com/baidu/hugegraph/util/Bytes.java
+++ b/src/main/java/com/baidu/hugegraph/util/Bytes.java
@@ -85,6 +85,10 @@ public final class Bytes {
         return Arrays.equals(bytes1, bytes2);
     }
 
+    public static String toHex(byte b) {
+        return toHex(new byte[]{b});
+    }
+
     public static String toHex(byte[] bytes) {
         return new String(Hex.encodeHex(bytes));
     }
diff --git a/src/main/java/com/baidu/hugegraph/version/CommonVersion.java b/src/main/java/com/baidu/hugegraph/version/CommonVersion.java
index 1a8bddea3..b5c0dbeac 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,
-                                                     "1.6.11");
+                                                     "1.6.12");
 }
diff --git a/src/test/java/com/baidu/hugegraph/unit/util/BytesTest.java b/src/test/java/com/baidu/hugegraph/unit/util/BytesTest.java
index bfb19ceff..c3d2cb1dd 100644
--- a/src/test/java/com/baidu/hugegraph/unit/util/BytesTest.java
+++ b/src/test/java/com/baidu/hugegraph/unit/util/BytesTest.java
@@ -137,6 +137,21 @@ public class BytesTest extends BaseUnitTest {
         Assert.assertEquals(-1, Bytes.indexOf(b(""), (byte) '0'));
     }
 
+    @Test
+    public void testByteToHex() {
+        byte value = 0;
+        Assert.assertEquals("00", Bytes.toHex(value));
+
+        value = 127;
+        Assert.assertEquals("7f", Bytes.toHex(value));
+
+        value = -128;
+        Assert.assertEquals("80", Bytes.toHex(value));
+
+        value = -1;
+        Assert.assertEquals("ff", Bytes.toHex(value));
+    }
+
     @Test
     public void testBytesToHex() {
         int value = 0x0103807f;