diff --git a/src/cpp/ripple/SerializedTransaction.cpp b/src/cpp/ripple/SerializedTransaction.cpp
index 0d7dd34f2..ccd5f073e 100644
--- a/src/cpp/ripple/SerializedTransaction.cpp
+++ b/src/cpp/ripple/SerializedTransaction.cpp
@@ -11,7 +11,8 @@
 SETUP_LOG();
 DECLARE_INSTANCE(SerializedTransaction);
 
-SerializedTransaction::SerializedTransaction(TransactionType type) : STObject(sfTransaction), mType(type)
+SerializedTransaction::SerializedTransaction(TransactionType type) : STObject(sfTransaction), mType(type),
+	mSigGood(false), mSigBad(false)
 {
 	mFormat = TransactionFormat::getTxnFormat(type);
 	if (mFormat == NULL)
@@ -23,7 +24,8 @@ SerializedTransaction::SerializedTransaction(TransactionType type) : STObject(sf
 	setFieldU16(sfTransactionType, mFormat->t_type);
 }
 
-SerializedTransaction::SerializedTransaction(const STObject& object) : STObject(object)
+SerializedTransaction::SerializedTransaction(const STObject& object) : STObject(object),
+	mSigGood(false), mSigBad(false)
 {
 	mType = static_cast<TransactionType>(getFieldU16(sfTransactionType));
 	mFormat = TransactionFormat::getTxnFormat(mType);
@@ -38,7 +40,8 @@ SerializedTransaction::SerializedTransaction(const STObject& object) : STObject(
 	}
 }
 
-SerializedTransaction::SerializedTransaction(SerializerIterator& sit) : STObject(sfTransaction)
+SerializedTransaction::SerializedTransaction(SerializerIterator& sit) : STObject(sfTransaction),
+	mSigGood(false), mSigBad(false)
 {
 	int length = sit.getBytesLeft();
 	if ((length < TransactionMinLen) || (length > TransactionMaxLen))
@@ -156,16 +159,28 @@ void SerializedTransaction::sign(const RippleAddress& naAccountPrivate)
 
 bool SerializedTransaction::checkSign() const
 {
+	if (mSigGood)
+		return true;
+
+	if (mSigBad)
+		return false;
+
 	try
 	{
 		RippleAddress n;
 		n.setAccountPublic(getFieldVL(sfSigningPubKey));
-		return checkSign(n);
+		if (checkSign(n))
+		{
+			mSigGood = true;
+			return true;
+		}
 	}
 	catch (...)
 	{
-		return false;
+		;
 	}
+	mSigBad = true;
+	return false;
 }
 
 bool SerializedTransaction::checkSign(const RippleAddress& naAccountPublic) const
diff --git a/src/cpp/ripple/SerializedTransaction.h b/src/cpp/ripple/SerializedTransaction.h
index 5dfc24f27..6b9dde135 100644
--- a/src/cpp/ripple/SerializedTransaction.h
+++ b/src/cpp/ripple/SerializedTransaction.h
@@ -32,6 +32,8 @@ protected:
 
 	SerializedTransaction* duplicate() const { return new SerializedTransaction(*this); }
 
+	mutable bool mSigGood, mSigBad;
+
 public:
 	SerializedTransaction(SerializerIterator& sit);
 	SerializedTransaction(TransactionType type);
@@ -69,6 +71,10 @@ public:
 	void sign(const RippleAddress& naAccountPrivate);
 	bool checkSign(const RippleAddress& naAccountPublic) const;
 	bool checkSign() const;
+	bool isKnownGood() const 	{ return mSigGood; }
+	bool isKnownBad() const		{ return mSigBad; }
+	void setGood() const		{ mSigGood = true; }
+	void setBad() const			{ mSigBad = true; }
 
 	// SQL Functions
 	static std::string getSQLValueHeader();