diff --git a/libethereum/State.cpp b/libethereum/State.cpp
index 7d27520dd..e9e21d9fe 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
-			myMemory.erase(_n);
+		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;