diff --git a/BUILDING.md b/BUILDING.md
index f7b65cd47..56174cbf8 100644
--- a/BUILDING.md
+++ b/BUILDING.md
@@ -13,7 +13,7 @@ A decent C++11 compiler (I use GNU GCC 4.8.1). CMake, version 2.8 or greater.
 
 On Ubuntu:
 
-	sudo apt-get install libgmp3-dev libcrypto++-dev libssl-dev libboost-all-dev cmake libleveldb-dev
+	sudo apt-get install libgmp3-dev libcrypto++-dev libssl-dev libboost-all-dev cmake libleveldb-dev  libminiupnpc-dev
 
 ## Building
 
diff --git a/libethereum/PeerNetwork.cpp b/libethereum/PeerNetwork.cpp
index 597e2d45e..97f782e3a 100644
--- a/libethereum/PeerNetwork.cpp
+++ b/libethereum/PeerNetwork.cpp
@@ -959,7 +959,7 @@ bool PeerServer::process(BlockChain& _bc, TransactionQueue& _tq, Overlay& _o)
 			}
 			m_latestBlockSent = h;
 
-			for (bool accepted = 1; accepted;)
+			for (int accepted = 1; accepted;)
 			{
 				accepted = 0;
 				if (m_incomingBlocks.size())
diff --git a/libethereum/PeerNetwork.h b/libethereum/PeerNetwork.h
index 3aa794450..aeeaae725 100644
--- a/libethereum/PeerNetwork.h
+++ b/libethereum/PeerNetwork.h
@@ -117,7 +117,7 @@ enum class NodeMode
 	PeerServer
 };
 
-class UPnP;
+struct UPnP;
 
 class PeerServer
 {
diff --git a/libethereum/RLP.h b/libethereum/RLP.h
index 0a586dd21..9b563ed4e 100644
--- a/libethereum/RLP.h
+++ b/libethereum/RLP.h
@@ -169,7 +169,7 @@ public:
 	/// Converts to bytearray. @returns the empty byte array if not a string.
 	bytes toBytes() const { if (!isString()) return bytes(); return bytes(payload().data(), payload().data() + items()); }
 	/// Converts to bytearray. @returns the empty byte array if not a string.
-	bytesConstRef toBytesConstRef() const { if (!isString()) return bytesConstRef(); payload().cropped(0, items()); }
+	bytesConstRef toBytesConstRef() const { if (!isString()) return bytesConstRef(); return payload().cropped(0, items()); }
 	/// Converts to string. @returns the empty string if not a string.
 	std::string toString() const { if (!isString()) return std::string(); return payload().cropped(0, items()).toString(); }
 	/// Converts to string. @throws BadCast if not a string.
diff --git a/libethereum/State.cpp b/libethereum/State.cpp
index 7d27520dd..fd3c68f98 100644
--- a/libethereum/State.cpp
+++ b/libethereum/State.cpp
@@ -103,7 +103,10 @@ void State::ensureCached(Address _a, bool _requireMemory, bool _forceCreate) con
 		TrieDB<u256, Overlay> memdb(const_cast<Overlay*>(&m_db), it->second.oldRoot());		// promise we won't alter the overlay! :)
 		map<u256, u256>& mem = it->second.takeMemory();
 		for (auto const& i: memdb)
-			mem[i.first] = RLP(i.second).toInt<u256>();
+			if(mem.find(i.first)==mem.end())
+				mem.insert(std::pair<u256,u256>(i.first,RLP(i.second).toInt<u256>()));
+			else
+				mem.at(i.first) = RLP(i.second).toInt<u256>();
 	}
 }
 
@@ -565,7 +568,11 @@ void State::executeBare(Transaction const& _t, Address _sender)
 		m_cache[newAddress] = AddressState(0, 0, sha3(RLPNull));
 		auto& mem = m_cache[newAddress].takeMemory();
 		for (uint i = 0; i < _t.data.size(); ++i)
-			mem[i] = _t.data[i];
+			if(mem.find(i)==mem.end())
+				mem.insert(std::pair<u256,u256>(i,_t.data[i]));
+			else
+				mem.at(i) = _t.data[i];
+        
 		subBalance(_sender, _t.value + _t.fee);
 		addBalance(newAddress, _t.value);
 		addBalance(m_currentBlock.coinbaseAddress, _t.fee);
@@ -600,10 +607,14 @@ void State::execute(Address _myAddress, Address _txSender, u256 _txValue, u256 _
 	};
 	auto setMem = [&](u256 _n, u256 _v)
 	{
-		if (_v)
-			myMemory[_n] = _v;
-		else
+		if (_v) {
+			if(myMemory.find(_n)==myMemory.end())
+				myMemory.insert(std::pair<u256,u256>(_n,_v));
+			else
+				myMemory.at(_n) = _v;
+		} else {
 			myMemory.erase(_n);
+		}
 	};
 
 	u256 curPC = 0;