diff --git a/src/cpp/ripple/AccountSetTransactor.cpp b/src/cpp/ripple/AccountSetTransactor.cpp
index 08f2bedaf..7808dcdb6 100644
--- a/src/cpp/ripple/AccountSetTransactor.cpp
+++ b/src/cpp/ripple/AccountSetTransactor.cpp
@@ -8,13 +8,50 @@ TER AccountSetTransactor::doApply()
 
 	const uint32	uTxFlags	= mTxn.getFlags();
 
+#if ENABLE_REQUIRE_DEST_TAG
+	const uint32	uFlagsIn	= mTxnAccount->getFieldU32(sfFlags);
+	uint32			uFlagsOut	= uFlagsIn;
+
+	if (uTxFlags & tfAccountSetMask)
+#else
 	if (uTxFlags)
+#endif
 	{
 		cLog(lsINFO) << "AccountSet: Malformed transaction: Invalid flags set.";
 
 		return temINVALID_FLAG;
 	}
 
+#if ENABLE_REQUIRE_DEST_TAG
+	//
+	// RequireDestTag
+	//
+
+	if ((tfRequireDestTag|tfOptionalDestTag) == (uTxFlags & (tfRequireDestTag|tfOptionalDestTag)))
+	{
+		cLog(lsINFO) << "AccountSet: Malformed transaction: Contradictory flags set.";
+
+		return temINVALID_FLAG;
+	}
+
+	if (uTxFlags & tfRequireDestTag)
+	{
+		cLog(lsINFO) << "AccountSet: Set RequireDestTag.";
+
+		uFlagsOut	|= lsfRequireDestTag;
+	}
+
+	if (uTxFlags & tfOptionalDestTag)
+	{
+		cLog(lsINFO) << "AccountSet: Clear RequireDestTag.";
+
+		uFlagsOut	&= ~lsfRequireDestTag;
+	}
+
+	if (uFlagsIn != uFlagsOut)
+		mTxnAccount->setFieldU32(sfFlags, uFlagsOut);
+#endif
+
 	//
 	// EmailHash
 	//
diff --git a/src/cpp/ripple/TransactionFormats.h b/src/cpp/ripple/TransactionFormats.h
index 6af1a74d9..333ede8a9 100644
--- a/src/cpp/ripple/TransactionFormats.h
+++ b/src/cpp/ripple/TransactionFormats.h
@@ -2,6 +2,7 @@
 #define __TRANSACTIONFORMATS__
 
 #include "SerializedObject.h"
+#include "LedgerFormats.h"
 
 enum TransactionType
 {
@@ -58,6 +59,13 @@ const int TransactionMaxLen			= 1048576;
 // Transaction flags.
 //
 
+#if ENABLE_REQUIRE_DEST_TAG
+// AccountSet flags:
+const uint32 tfRequireDestTag		= 0x00010000;
+const uint32 tfOptionalDestTag		= 0x00020000;
+const uint32 tfAccountSetMask		= ~(tfRequireDestTag|tfOptionalDestTag);
+#endif
+
 // OfferCreate flags:
 const uint32 tfPassive				= 0x00010000;
 const uint32 tfOfferCreateMask		= ~(tfPassive);