diff --git a/src/cpp/ripple/OfferCreateTransactor.cpp b/src/cpp/ripple/OfferCreateTransactor.cpp
index 27136b476..185e4fedb 100644
--- a/src/cpp/ripple/OfferCreateTransactor.cpp
+++ b/src/cpp/ripple/OfferCreateTransactor.cpp
@@ -244,8 +244,8 @@ TER OfferCreateTransactor::takeOffers(
 TER OfferCreateTransactor::doApply()
 {
 	Log(lsWARNING) << "doOfferCreate> " << mTxn.getJson(0);
-	const uint32			txFlags			= mTxn.getFlags();
-	const bool				bPassive		= isSetBit(txFlags, tfPassive);
+	const uint32			uTxFlags		= mTxn.getFlags();
+	const bool				bPassive		= isSetBit(uTxFlags, tfPassive);
 	STAmount				saTakerPays		= mTxn.getFieldAmount(sfTakerPays);
 	STAmount				saTakerGets		= mTxn.getFieldAmount(sfTakerGets);
 
@@ -273,7 +273,13 @@ TER OfferCreateTransactor::doApply()
 	uint64					uOwnerNode;
 	uint64					uBookNode;
 
-	if (bHaveExpiration && !uExpiration)
+	if (uTxFlags & tfOfferCreateMask)
+	{
+		Log(lsINFO) << "doOfferCreate: Malformed transaction: Invalid flags set.";
+
+		return temINVALID_FLAG;
+	}
+	else if (bHaveExpiration && !uExpiration)
 	{
 		Log(lsWARNING) << "doOfferCreate: Malformed offer: bad expiration";
 
diff --git a/src/cpp/ripple/TransactionFormats.h b/src/cpp/ripple/TransactionFormats.h
index ec0f4f887..091978ba1 100644
--- a/src/cpp/ripple/TransactionFormats.h
+++ b/src/cpp/ripple/TransactionFormats.h
@@ -56,6 +56,7 @@ const int TransactionMaxLen			= 1048576;
 
 // OfferCreate flags:
 const uint32 tfPassive				= 0x00010000;
+const uint32 tfOfferCreateMask		= ~(tfPassive);
 
 // Payment flags:
 const uint32 tfCreateAccount		= 0x00010000;