diff --git a/pom.xml b/pom.xml
index fc6ac2909..0bb469425 100644
--- a/pom.xml
+++ b/pom.xml
@@ -6,7 +6,7 @@
 
     <groupId>com.baidu.hugegraph</groupId>
     <artifactId>hugegraph-common</artifactId>
-    <version>1.6.10</version>
+    <version>1.6.11</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>1.6.10.0</Implementation-Version>
+                            <Implementation-Version>1.6.11.0</Implementation-Version>
                         </manifestEntries>
                     </archive>
                 </configuration>
diff --git a/src/main/java/com/baidu/hugegraph/util/LongEncoding.java b/src/main/java/com/baidu/hugegraph/util/LongEncoding.java
index 87b1366fa..4456cf517 100644
--- a/src/main/java/com/baidu/hugegraph/util/LongEncoding.java
+++ b/src/main/java/com/baidu/hugegraph/util/LongEncoding.java
@@ -70,11 +70,15 @@ public static long decodeSortable(String str) {
         E.checkArgument(str.length() >= 2,
                         "Length of sortable encoded string must be >=2");
         boolean negative = str.charAt(0) == NEG;
-        int prefix = 1;
+        int lengthPos = 0;
         if (negative) {
-            prefix = 2;
+            lengthPos = 1;
         }
-        String encoded = str.substring(prefix);
+        int length = BASE_SYMBOLS.indexOf(str.charAt(lengthPos));
+        E.checkArgument(length == str.length() - lengthPos - 1,
+                        "Can't decode illegal string '%s' with wrong length",
+                        str);
+        String encoded = str.substring(lengthPos + 1);
         long value = decode(encoded);
         if (negative) {
             value -= FULL_LONG;
@@ -82,6 +86,10 @@ public static long decodeSortable(String str) {
         return value;
     }
 
+    public static boolean validSortableChar(char c) {
+        return BASE_SYMBOLS.indexOf(c) != -1;
+    }
+
     public static String encode(long num) {
         return encode(num, BASE_SYMBOLS);
     }
diff --git a/src/main/java/com/baidu/hugegraph/version/CommonVersion.java b/src/main/java/com/baidu/hugegraph/version/CommonVersion.java
index a54b4186b..1a8bddea3 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,
-                                                     "1.6.10");
+                                                     "1.6.11");
 }
diff --git a/src/test/java/com/baidu/hugegraph/unit/util/LongEncodingTest.java b/src/test/java/com/baidu/hugegraph/unit/util/LongEncodingTest.java
index 13ca425da..3004d856c 100644
--- a/src/test/java/com/baidu/hugegraph/unit/util/LongEncodingTest.java
+++ b/src/test/java/com/baidu/hugegraph/unit/util/LongEncodingTest.java
@@ -278,6 +278,29 @@ public void testDecodeSortable() {
         Assert.assertEquals(Long.MIN_VALUE, valLongMin);
     }
 
+    @Test
+    public void testDecodeIllegalSortable() {
+        // Length is 1, actual length is 0
+        Assert.assertThrows(IllegalArgumentException.class, () -> {
+            LongEncoding.decodeSortable("1");
+        });
+
+        // Length is 1, actual length is 2
+        Assert.assertThrows(IllegalArgumentException.class, () -> {
+            LongEncoding.decodeSortable("123");
+        });
+
+        // Length is 1, actual length is 0
+        Assert.assertThrows(IllegalArgumentException.class, () -> {
+            LongEncoding.decodeSortable("01");
+        });
+
+        // Length is 1, actual length is 2
+        Assert.assertThrows(IllegalArgumentException.class, () -> {
+            LongEncoding.decodeSortable("0123");
+        });
+    }
+
     @Test
     public void testEncodeNumber() throws ParseException {
         String l1234 = LongEncoding.encodeNumber(1234);