diff --git a/java/src/main/java/org/msgpack/MessagePackObject.java b/java/src/main/java/org/msgpack/MessagePackObject.java
index b1a6faba..6181f7a3 100644
--- a/java/src/main/java/org/msgpack/MessagePackObject.java
+++ b/java/src/main/java/org/msgpack/MessagePackObject.java
@@ -119,6 +119,10 @@ public abstract class MessagePackObject implements Cloneable, MessagePackable {
 		throw new MessageTypeException("type error");
 	}
 
+	public BigInteger bigIntegerValue() {
+		throw new MessageTypeException("type error");
+	}
+
 	public float floatValue() {
 		throw new MessageTypeException("type error");
 	}
diff --git a/java/src/main/java/org/msgpack/object/BigIntegerTypeIMPL.java b/java/src/main/java/org/msgpack/object/BigIntegerTypeIMPL.java
index fd517e70..7b060eef 100644
--- a/java/src/main/java/org/msgpack/object/BigIntegerTypeIMPL.java
+++ b/java/src/main/java/org/msgpack/object/BigIntegerTypeIMPL.java
@@ -60,6 +60,11 @@ class BigIntegerTypeIMPL extends IntegerType {
 		return value.longValue();
 	}
 
+	@Override
+	public BigInteger asBigInteger() {
+		return value;
+	}
+
 	@Override
 	public byte byteValue() {
 		return value.byteValue();
@@ -80,6 +85,11 @@ class BigIntegerTypeIMPL extends IntegerType {
 		return value.longValue();
 	}
 
+	@Override
+	public BigInteger bigIntegerValue() {
+		return value;
+	}
+
 	@Override
 	public float floatValue() {
 		return value.floatValue();
@@ -98,6 +108,11 @@ class BigIntegerTypeIMPL extends IntegerType {
 	@Override
 	public boolean equals(Object obj) {
 		if(obj.getClass() != getClass()) {
+			if(obj.getClass() == ShortIntegerTypeIMPL.class) {
+				return BigInteger.valueOf((long)((ShortIntegerTypeIMPL)obj).shortValue()).equals(value);
+			} else if(obj.getClass() == LongIntegerTypeIMPL.class) {
+				return BigInteger.valueOf(((LongIntegerTypeIMPL)obj).longValue()).equals(value);
+			}
 			return false;
 		}
 		return ((BigIntegerTypeIMPL)obj).value.equals(value);
diff --git a/java/src/main/java/org/msgpack/object/DoubleTypeIMPL.java b/java/src/main/java/org/msgpack/object/DoubleTypeIMPL.java
index b47a7096..fd38089e 100644
--- a/java/src/main/java/org/msgpack/object/DoubleTypeIMPL.java
+++ b/java/src/main/java/org/msgpack/object/DoubleTypeIMPL.java
@@ -59,6 +59,11 @@ class DoubleTypeIMPL extends FloatType {
 		return (long)value;
 	}
 
+	@Override
+	public BigInteger bigIntegerValue() {
+		return BigInteger.valueOf((long)value);
+	}
+
 	@Override
 	public float floatValue() {
 		return (float)value;
diff --git a/java/src/main/java/org/msgpack/object/LongIntegerTypeIMPL.java b/java/src/main/java/org/msgpack/object/LongIntegerTypeIMPL.java
index 940ab6fa..3928a299 100644
--- a/java/src/main/java/org/msgpack/object/LongIntegerTypeIMPL.java
+++ b/java/src/main/java/org/msgpack/object/LongIntegerTypeIMPL.java
@@ -57,6 +57,11 @@ class LongIntegerTypeIMPL extends IntegerType {
 		return value;
 	}
 
+	@Override
+	public BigInteger asBigInteger() {
+		return BigInteger.valueOf(value);
+	}
+
 	@Override
 	public byte byteValue() {
 		return (byte)value;
@@ -77,6 +82,11 @@ class LongIntegerTypeIMPL extends IntegerType {
 		return (long)value;
 	}
 
+	@Override
+	public BigInteger bigIntegerValue() {
+		return BigInteger.valueOf(value);
+	}
+
 	@Override
 	public float floatValue() {
 		return (float)value;
@@ -95,6 +105,11 @@ class LongIntegerTypeIMPL extends IntegerType {
 	@Override
 	public boolean equals(Object obj) {
 		if(obj.getClass() != getClass()) {
+			if(obj.getClass() == ShortIntegerTypeIMPL.class) {
+				return value == ((ShortIntegerTypeIMPL)obj).longValue();
+			} else if(obj.getClass() == BigIntegerTypeIMPL.class) {
+				return (long)value == ((BigIntegerTypeIMPL)obj).longValue();
+			}
 			return false;
 		}
 		return ((LongIntegerTypeIMPL)obj).value == value;
diff --git a/java/src/main/java/org/msgpack/object/ShortIntegerTypeIMPL.java b/java/src/main/java/org/msgpack/object/ShortIntegerTypeIMPL.java
index 60e92b8e..dbed4263 100644
--- a/java/src/main/java/org/msgpack/object/ShortIntegerTypeIMPL.java
+++ b/java/src/main/java/org/msgpack/object/ShortIntegerTypeIMPL.java
@@ -79,6 +79,11 @@ class ShortIntegerTypeIMPL extends IntegerType {
 		return (long)value;
 	}
 
+	@Override
+	public BigInteger bigIntegerValue() {
+		return BigInteger.valueOf((long)value);
+	}
+
 	@Override
 	public float floatValue() {
 		return (float)value;
@@ -97,6 +102,11 @@ class ShortIntegerTypeIMPL extends IntegerType {
 	@Override
 	public boolean equals(Object obj) {
 		if(obj.getClass() != getClass()) {
+			if(obj.getClass() == LongIntegerTypeIMPL.class) {
+				return (long)value == ((LongIntegerTypeIMPL)obj).longValue();
+			} else if(obj.getClass() == BigIntegerTypeIMPL.class) {
+				return ((BigIntegerTypeIMPL)obj).bigIntegerValue().equals(BigInteger.valueOf((long)value));
+			}
 			return false;
 		}
 		return ((ShortIntegerTypeIMPL)obj).value == value;