diff --git a/libdevcrypto/MemoryDB.h b/libdevcrypto/MemoryDB.h
index 7d39ba73b..7858126f8 100644
--- a/libdevcrypto/MemoryDB.h
+++ b/libdevcrypto/MemoryDB.h
@@ -32,8 +32,10 @@ namespace dev
 {
 
 struct DBChannel: public LogChannel  { static const char* name() { return "TDB"; } static const int verbosity = 18; };
+struct DBWarn: public LogChannel  { static const char* name() { return "TDB"; } static const int verbosity = 1; };
 
 #define dbdebug clog(DBChannel)
+#define dbwarn clog(DBWarn)
 
 class MemoryDB
 {
diff --git a/libethereum/BlockChain.cpp b/libethereum/BlockChain.cpp
index 508531f9d..8c0bd2b8b 100644
--- a/libethereum/BlockChain.cpp
+++ b/libethereum/BlockChain.cpp
@@ -339,6 +339,13 @@ h256s BlockChain::import(bytes const& _block, OverlayDB const& _db)
 #endif
 		// All ok - insert into DB
 		{
+			// ensure parent is cached for later addition.
+			// TODO: this is a bit horrible would be better refactored into an enveloping UpgradableGuard
+			// together with an "ensureCachedWithUpdatableLock(l)" method.
+			// This is safe in practice since the caches don't get flushed nearly often enough to be
+			// done here.
+			details(bi.parentHash);
+
 			WriteGuard l(x_details);
 			m_details[newHash] = BlockDetails((unsigned)pd.number + 1, td, bi.parentHash, {});
 			m_details[bi.parentHash].children.push_back(newHash);
@@ -455,14 +462,14 @@ h256s BlockChain::import(bytes const& _block, OverlayDB const& _db)
 
 h256s BlockChain::treeRoute(h256 const& _from, h256 const& _to, h256* o_common, bool _pre, bool _post) const
 {
-	//	cdebug << "treeRoute" << _from.abridged() << "..." << _to.abridged();
+	cdebug << "treeRoute" << _from.abridged() << "..." << _to.abridged();
 	if (!_from || !_to)
 		return h256s();
 	h256s ret;
 	h256s back;
 	unsigned fn = details(_from).number;
 	unsigned tn = details(_to).number;
-	//	cdebug << "treeRoute" << fn << "..." << tn;
+	cdebug << "treeRoute" << fn << "..." << tn;
 	h256 from = _from;
 	while (fn > tn)
 	{
@@ -470,7 +477,7 @@ h256s BlockChain::treeRoute(h256 const& _from, h256 const& _to, h256* o_common,
 			ret.push_back(from);
 		from = details(from).parent;
 		fn--;
-		//		cdebug << "from:" << fn << _from.abridged();
+		cdebug << "from:" << fn << _from.abridged();
 	}
 	h256 to = _to;
 	while (fn < tn)
@@ -479,12 +486,14 @@ h256s BlockChain::treeRoute(h256 const& _from, h256 const& _to, h256* o_common,
 			back.push_back(to);
 		to = details(to).parent;
 		tn--;
-		//		cdebug << "to:" << tn << _to.abridged();
+		cdebug << "to:" << tn << _to.abridged();
 	}
 	while (from != to)
 	{
-		assert(from);
-		assert(to);
+		if (!from)
+			assert(from);
+		if (!to)
+			assert(to);
 		from = details(from).parent;
 		to = details(to).parent;
 		if (_pre)
diff --git a/libethereum/State.cpp b/libethereum/State.cpp
index c52c90921..fa457dc41 100644
--- a/libethereum/State.cpp
+++ b/libethereum/State.cpp
@@ -725,7 +725,7 @@ void State::commitToMine(BlockChain const& _bc)
 	uncommitToMine();
 
 //	cnote << "Committing to mine on block" << m_previousBlock.hash.abridged();
-#ifdef ETH_PARANOIA
+#if  ETH_PARANOIA && 0
 	commit();
 	cnote << "Pre-reward stateRoot:" << m_state.root();
 #endif