diff --git a/src/Ledger.cpp b/src/Ledger.cpp
index c93b905323..eb82d387f2 100644
--- a/src/Ledger.cpp
+++ b/src/Ledger.cpp
@@ -434,9 +434,7 @@ void Ledger::saveAcceptedLedger(bool fromConsensus)
 	theApp->getOPs().pubLedger(shared_from_this());
 
 	if(theConfig.FULL_HISTORY)
-	{
-		// WRITEME: check for seamless ledger history
-	}
+		theApp->getMasterLedger().checkLedgerGap(shared_from_this());
 
 }
 
diff --git a/src/LedgerAcquire.cpp b/src/LedgerAcquire.cpp
index 9cc09b2ee5..71c631eb06 100644
--- a/src/LedgerAcquire.cpp
+++ b/src/LedgerAcquire.cpp
@@ -647,6 +647,7 @@ void LedgerAcquireSet::onComplete(boost::weak_ptr<LedgerAcquireSet> set, LedgerA
 	{
 		Ledger::pointer ledger = acquired->getLedger();
 		ledger->setAccepted();
+		theApp->getMasterLedger().checkLedgerGap(ledger);
 		lSet->updateCurrentLedger(ledger);
 	}
 	else
diff --git a/src/LedgerAcquire.h b/src/LedgerAcquire.h
index cbd0459dc3..dc717efee3 100644
--- a/src/LedgerAcquire.h
+++ b/src/LedgerAcquire.h
@@ -137,8 +137,8 @@ public:
 	void dropLedger(const uint256& ledgerHash);
 	bool gotLedgerData(ripple::TMLedgerData& packet, Peer::ref);
 
-	void killSet(const LedgerAcquireSet&)
-	{ mAcquireSet = LedgerAcquireSet::pointer(); }
+	bool hasSet()							{ return !!mAcquireSet; }
+	void killSet(const LedgerAcquireSet&)	{ mAcquireSet = LedgerAcquireSet::pointer(); }
 	void makeSet(Ledger::ref target, Ledger::ref current)
 	{ mAcquireSet = boost::make_shared<LedgerAcquireSet>(boost::ref(target), boost::ref(current)); }
 };
diff --git a/src/LedgerMaster.cpp b/src/LedgerMaster.cpp
index 773e98dbed..83e2cdc3b6 100644
--- a/src/LedgerMaster.cpp
+++ b/src/LedgerMaster.cpp
@@ -23,7 +23,7 @@ void LedgerMaster::pushLedger(Ledger::ref newLedger)
 	// Caller should already have properly assembled this ledger into "ready-to-close" form --
 	// all candidate transactions must already be applied
 	Log(lsINFO) << "PushLedger: " << newLedger->getHash();
-	ScopedLock sl(mLock);
+	boost::recursive_mutex::scoped_lock ml(mLock);
 	if (!!mFinalizedLedger)
 	{
 		mFinalizedLedger->setClosed();
@@ -51,8 +51,8 @@ void LedgerMaster::pushLedger(Ledger::ref newLCL, Ledger::ref newOL)
 		Log(lsINFO) << "StashAccepted: " << newLCL->getHash();
 	}
 
+	boost::recursive_mutex::scoped_lock ml(mLock);
 	mFinalizedLedger = newLCL;
-	ScopedLock sl(mLock);
 	mCurrentLedger = newOL;
 	mEngine.setLedger(newOL);
 }
@@ -60,11 +60,15 @@ void LedgerMaster::pushLedger(Ledger::ref newLCL, Ledger::ref newOL)
 void LedgerMaster::switchLedgers(Ledger::ref lastClosed, Ledger::ref current)
 {
 	assert(lastClosed && current);
-	mFinalizedLedger = lastClosed;
-	mFinalizedLedger->setClosed();
-	mFinalizedLedger->setAccepted();
 
-	mCurrentLedger = current;
+	{
+		boost::recursive_mutex::scoped_lock ml(mLock);
+		mFinalizedLedger = lastClosed;
+		mFinalizedLedger->setClosed();
+		mFinalizedLedger->setAccepted();
+		mCurrentLedger = current;
+	}
+
 	assert(!mCurrentLedger->isClosed());
 	mEngine.setLedger(mCurrentLedger);
 }
@@ -77,7 +81,6 @@ void LedgerMaster::storeLedger(Ledger::ref ledger)
 }
 
 
-
 Ledger::pointer LedgerMaster::closeLedger()
 {
 	boost::recursive_mutex::scoped_lock sl(mLock);
@@ -94,5 +97,25 @@ TER LedgerMaster::doTransaction(const SerializedTransaction& txn, TransactionEng
 	return result;
 }
 
+void LedgerMaster::checkLedgerGap(Ledger::ref ledger)
+{
+	boost::recursive_mutex::scoped_lock sl(mLock);
+
+	if (ledger->getParentHash() == mLastFullLedger->getHash())
+	{
+		mLastFullLedger = ledger;
+		return;
+	}
+
+	if (theApp->getMasterLedgerAcquire().hasSet())
+		return;
+
+	if (ledger->getLedgerSeq() < mLastFullLedger->getLedgerSeq())
+		return;
+
+	// we have a gap or discontinuity
+	theApp->getMasterLedgerAcquire().makeSet(mLastFullLedger, ledger);
+
+}
 
 // vim:ts=4
diff --git a/src/LedgerMaster.h b/src/LedgerMaster.h
index 36f9339db5..47cf394b50 100644
--- a/src/LedgerMaster.h
+++ b/src/LedgerMaster.h
@@ -52,9 +52,12 @@ public:
 
 	void setLastFullLedger(Ledger::ref ledger)
 	{
+		boost::recursive_mutex::scoped_lock ml(mLock);
 		mLastFullLedger = ledger;
 	}
 
+	void checkLedgerGap(Ledger::ref ledger);
+
 	void switchLedgers(Ledger::ref lastClosed, Ledger::ref newCurrent);
 
 	Ledger::pointer closeLedger();