diff --git a/eth/main.cpp b/eth/main.cpp
index 235183ef6..64679762d 100644
--- a/eth/main.cpp
+++ b/eth/main.cpp
@@ -820,7 +820,7 @@ int main(int argc, char** argv)
 
 		while (web3.ethereum()->blockQueue().items().first + web3.ethereum()->blockQueue().items().second > 0)
 		{
-			sleep(1);
+			this_thread::sleep_for(chrono::seconds(1));
 			web3.ethereum()->syncQueue(100000);
 		}
 		double e = chrono::duration_cast<chrono::milliseconds>(chrono::steady_clock::now() - t).count() / 1000.0;
diff --git a/libethash-cl/ethash_cl_miner.cpp b/libethash-cl/ethash_cl_miner.cpp
index 79024e2ad..b12e4d9f8 100644
--- a/libethash-cl/ethash_cl_miner.cpp
+++ b/libethash-cl/ethash_cl_miner.cpp
@@ -24,13 +24,13 @@
 
 #include <cstdio>
 #include <cstdlib>
+#include <chrono>
 #include <fstream>
 #include <iostream>
 #include <assert.h>
 #include <queue>
 #include <random>
 #include <vector>
-#include <boost/timer.hpp>
 #include <libethash/util.h>
 #include <libethash/ethash.h>
 #include <libethash/internal.h>
@@ -416,6 +416,7 @@ bool ethash_cl_miner::init(
 
 void ethash_cl_miner::search(uint8_t const* header, uint64_t target, search_hook& hook, unsigned _msPerBatch)
 {
+	(void)_msPerBatch;
 	try
 	{
 		struct pending_batch
@@ -454,6 +455,8 @@ void ethash_cl_miner::search(uint8_t const* header, uint64_t target, search_hook
 		uint64_t start_nonce = uniform_int_distribution<uint64_t>()(engine);
 		for (;; start_nonce += m_batchSize)
 		{
+//			chrono::high_resolution_clock::time_point t = chrono::high_resolution_clock::now();
+
 			// supply output buffer to kernel
 			m_searchKernel.setArg(0, m_searchBuffer[buf]);
 			if (m_dagChunksCount == 1)
@@ -462,13 +465,7 @@ void ethash_cl_miner::search(uint8_t const* header, uint64_t target, search_hook
 				m_searchKernel.setArg(6, start_nonce);
 
 			// execute it!
-			boost::timer t;
 			m_queue.enqueueNDRangeKernel(m_searchKernel, cl::NullRange, m_batchSize, m_workgroupSize);
-			unsigned ms = t.elapsed() * 1000;
-			if (ms > _msPerBatch * 1.1)
-				m_batchSize = max<unsigned>(128, m_batchSize * 9 / 10);
-			else if (ms < _msPerBatch * 0.9)
-				m_batchSize = m_batchSize * 10 / 9;
 
 			pending.push({ start_nonce, buf });
 			buf = (buf + 1) % c_bufferCount;
@@ -498,6 +495,20 @@ void ethash_cl_miner::search(uint8_t const* header, uint64_t target, search_hook
 
 				pending.pop();
 			}
+
+/*			chrono::high_resolution_clock::duration d = chrono::high_resolution_clock::now() - t;
+			if (d > chrono::milliseconds(_msPerBatch * 10 / 9))
+			{
+				cerr << "Batch of" << m_batchSize << "took" << chrono::duration_cast<chrono::milliseconds>(d).count() << "ms, >>" << _msPerBatch << "ms.";
+				m_batchSize = max<unsigned>(128, m_batchSize * 9 / 10);
+				cerr << "New batch size" << m_batchSize;
+			}
+			else if (d < chrono::milliseconds(_msPerBatch * 9 / 10))
+			{
+				cerr << "Batch of" << m_batchSize << "took" << chrono::duration_cast<chrono::milliseconds>(d).count() << "ms, <<" << _msPerBatch << "ms.";
+				m_batchSize = m_batchSize * 10 / 9;
+				cerr << "New batch size" << m_batchSize;
+			}*/
 		}
 
 		// not safe to return until this is ready
diff --git a/libethcore/Common.h b/libethcore/Common.h
index 25a6a8e1d..732d09981 100644
--- a/libethcore/Common.h
+++ b/libethcore/Common.h
@@ -112,6 +112,7 @@ enum class ImportResult
 	AlreadyInChain,
 	AlreadyKnown,
 	Malformed,
+	OverbidGasPrice,
 	BadChain
 };
 
diff --git a/libethereum/BlockChain.cpp b/libethereum/BlockChain.cpp
index 7abf9316e..9bf89665a 100644
--- a/libethereum/BlockChain.cpp
+++ b/libethereum/BlockChain.cpp
@@ -400,7 +400,6 @@ ImportRoute BlockChain::import(bytes const& _block, OverlayDB const& _db, Import
 //		clog(BlockChainNote) << "   Malformed block: " << diagnostic_information(ex);
 		ex << errinfo_phase(2);
 		ex << errinfo_now(time(0));
-		ex << errinfo_block(_block);
 		throw;
 	}
 #endif
@@ -1127,6 +1126,8 @@ VerifiedBlockRef BlockChain::verifyBlock(bytes const& _block, function<void(Exce
 			ex << errinfo_transactionIndex(i);
 			ex << errinfo_transaction(d.toBytes());
 			ex << errinfo_block(_block);
+			if (_onBad)
+				_onBad(ex);
 			throw;
 		}
 		++i;
diff --git a/libethereum/Client.cpp b/libethereum/Client.cpp
index ad551c2ec..2b0a64491 100644
--- a/libethereum/Client.cpp
+++ b/libethereum/Client.cpp
@@ -105,7 +105,8 @@ void Client::onBadBlock(Exception& _ex) const
 	bytes const* block = boost::get_error_info<errinfo_block>(_ex);
 	if (!block)
 	{
-		cwarn << "ODD: onBadBlock called but exception has no block in it.";
+		cwarn << "ODD: onBadBlock called but exception (" << _ex.what() << ") has no block in it.";
+		cwarn << boost::diagnostic_information(_ex, true);
 		return;
 	}
 
diff --git a/libethereum/TransactionQueue.cpp b/libethereum/TransactionQueue.cpp
index a86f6abf3..8931ee218 100644
--- a/libethereum/TransactionQueue.cpp
+++ b/libethereum/TransactionQueue.cpp
@@ -113,6 +113,26 @@ ImportResult TransactionQueue::manageImport_WITH_LOCK(h256 const& _h, Transactio
 		// If it doesn't work, the signature is bad.
 		// The transaction's nonce may yet be invalid (or, it could be "valid" but we may be missing a marginally older transaction).
 
+		auto r = m_senders.equal_range(_transaction.from());
+		for (auto it = r.first; it != r.second; ++it)
+			if (m_current.count(it->second) && m_current[it->second].nonce() == _transaction.nonce())
+				if (_transaction.gasPrice() < m_current[it->second].gasPrice())
+					return ImportResult::OverbidGasPrice;
+				else
+				{
+					remove_WITH_LOCK(it->second);
+					break;
+				}
+			else if (m_future.count(it->second) && m_future[it->second].nonce() == _transaction.nonce())
+				if (_transaction.gasPrice() < m_future[it->second].gasPrice())
+					return ImportResult::OverbidGasPrice;
+				else
+				{
+					remove_WITH_LOCK(it->second);
+					break;
+				}
+			else {}
+
 		// If valid, append to blocks.
 		insertCurrent_WITH_LOCK(make_pair(_h, _transaction));
 		m_known.insert(_h);
diff --git a/libp2p/Session.cpp b/libp2p/Session.cpp
index 0c35293f6..1268b865c 100644
--- a/libp2p/Session.cpp
+++ b/libp2p/Session.cpp
@@ -212,11 +212,12 @@ bool Session::interpret(PacketType _t, RLP const& _r)
 	}
 	case PongPacket:
 		DEV_GUARDED(x_info)
-		m_info.lastPing = std::chrono::steady_clock::now() - m_ping;
-		clog(NetTriviaSummary) << "Latency: " << chrono::duration_cast<chrono::milliseconds>(m_info.lastPing).count() << " ms";
+		{
+			m_info.lastPing = std::chrono::steady_clock::now() - m_ping;
+			clog(NetTriviaSummary) << "Latency: " << chrono::duration_cast<chrono::milliseconds>(m_info.lastPing).count() << " ms";
+		}
 		break;
 	case GetPeersPacket:
-		break;
 	case PeersPacket:
 		break;
 	default:
diff --git a/libsolidity/AST.cpp b/libsolidity/AST.cpp
index 7333c024a..09af49c67 100644
--- a/libsolidity/AST.cpp
+++ b/libsolidity/AST.cpp
@@ -340,8 +340,10 @@ vector<pair<FixedHash<4>, FunctionTypePointer>> const& ContractDefinition::getIn
 		{
 			for (ASTPointer<FunctionDefinition> const& f: contract->getDefinedFunctions())
 			{
+				if (!f->isPartOfExternalInterface())
+					continue;
 				string functionSignature = f->externalSignature();
-				if (f->isPartOfExternalInterface() && signaturesSeen.count(functionSignature) == 0)
+				if (signaturesSeen.count(functionSignature) == 0)
 				{
 					functionsSeen.insert(f->getName());
 					signaturesSeen.insert(functionSignature);
diff --git a/libsolidity/ArrayUtils.cpp b/libsolidity/ArrayUtils.cpp
index 3be12af72..f13b28173 100644
--- a/libsolidity/ArrayUtils.cpp
+++ b/libsolidity/ArrayUtils.cpp
@@ -134,14 +134,14 @@ void ArrayUtils::copyArrayToStorage(ArrayType const& _targetType, ArrayType cons
 	if (sourceBaseType->getCategory() == Type::Category::Array)
 	{
 		solAssert(byteOffsetSize == 0, "Byte offset for array as base type.");
+		auto const& sourceBaseArrayType = dynamic_cast<ArrayType const&>(*sourceBaseType);
 		m_context << eth::Instruction::DUP3;
 		if (sourceIsStorage)
 			m_context << u256(0);
+		else if (sourceBaseArrayType.location() == DataLocation::Memory)
+			m_context << eth::Instruction::MLOAD;
 		m_context << eth::dupInstruction(sourceIsStorage ? 4 : 3) << u256(0);
-		copyArrayToStorage(
-			dynamic_cast<ArrayType const&>(*targetBaseType),
-			dynamic_cast<ArrayType const&>(*sourceBaseType)
-		);
+		copyArrayToStorage(dynamic_cast<ArrayType const&>(*targetBaseType), sourceBaseArrayType);
 		m_context << eth::Instruction::POP << eth::Instruction::POP;
 	}
 	else if (directCopy)
@@ -188,11 +188,18 @@ void ArrayUtils::copyArrayToStorage(ArrayType const& _targetType, ArrayType cons
 	if (haveByteOffsetSource)
 		incrementByteOffset(sourceBaseType->getStorageBytes(), 1, haveByteOffsetTarget ? 5 : 4);
 	else
+	{
+		m_context << eth::swapInstruction(2 + byteOffsetSize);
+		if (sourceIsStorage)
+			m_context << sourceBaseType->getStorageSize();
+		else if (_sourceType.location() == DataLocation::Memory)
+			m_context << sourceBaseType->memoryHeadSize();
+		else
+			m_context << sourceBaseType->getCalldataEncodedSize(true);
 		m_context
-			<< eth::swapInstruction(2 + byteOffsetSize)
-			<< (sourceIsStorage ? sourceBaseType->getStorageSize() : sourceBaseType->getCalldataEncodedSize())
 			<< eth::Instruction::ADD
 			<< eth::swapInstruction(2 + byteOffsetSize);
+	}
 	// increment target
 	if (haveByteOffsetTarget)
 		incrementByteOffset(targetBaseType->getStorageBytes(), byteOffsetSize, byteOffsetSize + 2);
@@ -235,8 +242,9 @@ void ArrayUtils::copyArrayToMemory(const ArrayType& _sourceType, bool _padToWord
 {
 	solAssert(
 		_sourceType.getBaseType()->getCalldataEncodedSize() > 0,
-		"Nested arrays not yet implemented here."
+		"Nested dynamic arrays not implemented here."
 	);
+	CompilerUtils utils(m_context);
 	unsigned baseSize = 1;
 	if (!_sourceType.isByteArray())
 		// We always pad the elements, regardless of _padToWordBoundaries.
@@ -246,7 +254,7 @@ void ArrayUtils::copyArrayToMemory(const ArrayType& _sourceType, bool _padToWord
 	{
 		if (!_sourceType.isDynamicallySized())
 			m_context << _sourceType.getLength();
-		if (_sourceType.getBaseType()->getCalldataEncodedSize() > 1)
+		if (baseSize > 1)
 			m_context << u256(baseSize) << eth::Instruction::MUL;
 		// stack: target source_offset source_len
 		m_context << eth::Instruction::DUP1 << eth::Instruction::DUP3 << eth::Instruction::DUP5;
@@ -257,8 +265,36 @@ void ArrayUtils::copyArrayToMemory(const ArrayType& _sourceType, bool _padToWord
 	}
 	else if (_sourceType.location() == DataLocation::Memory)
 	{
-		// memcpy using the built-in contract
 		retrieveLength(_sourceType);
+		// stack: target source length
+		if (!_sourceType.getBaseType()->isValueType())
+		{
+			// copy using a loop
+			m_context << u256(0) << eth::Instruction::SWAP3;
+			// stack: counter source length target
+			auto repeat = m_context.newTag();
+			m_context << repeat;
+			m_context << eth::Instruction::DUP2 << eth::Instruction::DUP5;
+			m_context << eth::Instruction::LT << eth::Instruction::ISZERO;
+			auto loopEnd = m_context.appendConditionalJump();
+			m_context << eth::Instruction::DUP3 << eth::Instruction::DUP5;
+			accessIndex(_sourceType, false);
+			MemoryItem(m_context, *_sourceType.getBaseType(), true).retrieveValue(SourceLocation(), true);
+			if (auto baseArray = dynamic_cast<ArrayType const*>(_sourceType.getBaseType().get()))
+				copyArrayToMemory(*baseArray, _padToWordBoundaries);
+			else
+				utils.storeInMemoryDynamic(*_sourceType.getBaseType());
+			m_context << eth::Instruction::SWAP3 << u256(1) << eth::Instruction::ADD;
+			m_context << eth::Instruction::SWAP3;
+			m_context.appendJumpTo(repeat);
+			m_context << loopEnd;
+			m_context << eth::Instruction::SWAP3;
+			utils.popStackSlots(3);
+			// stack: updated_target_pos
+			return;
+		}
+
+		// memcpy using the built-in contract
 		if (_sourceType.isDynamicallySized())
 		{
 			// change pointer to data part
@@ -271,7 +307,7 @@ void ArrayUtils::copyArrayToMemory(const ArrayType& _sourceType, bool _padToWord
 		// stack: <target> <source> <size>
 		//@TODO do not use ::CALL if less than 32 bytes?
 		m_context << eth::Instruction::DUP1 << eth::Instruction::DUP4 << eth::Instruction::DUP4;
-		CompilerUtils(m_context).memoryCopy();
+		utils.memoryCopy();
 
 		m_context << eth::Instruction::SWAP1 << eth::Instruction::POP;
 		// stack: <target> <size>
@@ -345,7 +381,7 @@ void ArrayUtils::copyArrayToMemory(const ArrayType& _sourceType, bool _padToWord
 		{
 			// actual array data is stored at SHA3(storage_offset)
 			m_context << eth::Instruction::SWAP1;
-			CompilerUtils(m_context).computeHashStatic();
+			utils.computeHashStatic();
 			m_context << eth::Instruction::SWAP1;
 		}
 
@@ -375,7 +411,10 @@ void ArrayUtils::copyArrayToMemory(const ArrayType& _sourceType, bool _padToWord
 			else
 				m_context << eth::Instruction::DUP2 << u256(0);
 			StorageItem(m_context, *_sourceType.getBaseType()).retrieveValue(SourceLocation(), true);
-			CompilerUtils(m_context).storeInMemoryDynamic(*_sourceType.getBaseType());
+			if (auto baseArray = dynamic_cast<ArrayType const*>(_sourceType.getBaseType().get()))
+				copyArrayToMemory(*baseArray, _padToWordBoundaries);
+			else
+				utils.storeInMemoryDynamic(*_sourceType.getBaseType());
 			// increment storage_data_offset and byte offset
 			if (haveByteOffset)
 				incrementByteOffset(storageBytes, 2, 3);
@@ -387,7 +426,8 @@ void ArrayUtils::copyArrayToMemory(const ArrayType& _sourceType, bool _padToWord
 			}
 		}
 		// check for loop condition
-		m_context << eth::Instruction::DUP1 << eth::dupInstruction(haveByteOffset ? 5 : 4) << eth::Instruction::GT;
+		m_context << eth::Instruction::DUP1 << eth::dupInstruction(haveByteOffset ? 5 : 4);
+		m_context << eth::Instruction::GT;
 		m_context.appendConditionalJumpTo(loopStart);
 		// stack here: memory_end_offset storage_data_offset [storage_byte_offset] memory_offset
 		if (haveByteOffset)
@@ -597,12 +637,14 @@ void ArrayUtils::convertLengthToSize(ArrayType const& _arrayType, bool _pad) con
 	}
 	else
 	{
-		solAssert(
-			_arrayType.getBaseType()->getCalldataEncodedSize() > 0,
-			"Copying nested dynamic arrays not yet implemented."
-		);
 		if (!_arrayType.isByteArray())
-			m_context << _arrayType.getBaseType()->getCalldataEncodedSize() << eth::Instruction::MUL;
+		{
+			if (_arrayType.location() == DataLocation::Memory)
+				m_context << _arrayType.getBaseType()->memoryHeadSize();
+			else
+				m_context << _arrayType.getBaseType()->getCalldataEncodedSize();
+			m_context << eth::Instruction::MUL;
+		}
 		else if (_pad)
 			m_context << u256(31) << eth::Instruction::ADD
 				<< u256(32) << eth::Instruction::DUP1
@@ -632,7 +674,7 @@ void ArrayUtils::retrieveLength(ArrayType const& _arrayType) const
 	}
 }
 
-void ArrayUtils::accessIndex(ArrayType const& _arrayType) const
+void ArrayUtils::accessIndex(ArrayType const& _arrayType, bool _doBoundsCheck) const
 {
 	DataLocation location = _arrayType.location();
 	eth::Instruction load =
@@ -640,19 +682,25 @@ void ArrayUtils::accessIndex(ArrayType const& _arrayType) const
 		location == DataLocation::Memory ? eth::Instruction::MLOAD :
 		eth::Instruction::CALLDATALOAD;
 
-	// retrieve length
-	if (!_arrayType.isDynamicallySized())
-		m_context << _arrayType.getLength();
-	else if (location == DataLocation::CallData)
-		// length is stored on the stack
-		m_context << eth::Instruction::SWAP1;
-	else
-		m_context << eth::Instruction::DUP2 << load;
-	// stack: <base_ref> <index> <length>
-	// check out-of-bounds access
-	m_context << eth::Instruction::DUP2 << eth::Instruction::LT << eth::Instruction::ISZERO;
-	// out-of-bounds access throws exception
-	m_context.appendConditionalJumpTo(m_context.errorTag());
+	if (_doBoundsCheck)
+	{
+		// retrieve length
+		if (!_arrayType.isDynamicallySized())
+			m_context << _arrayType.getLength();
+		else if (location == DataLocation::CallData)
+			// length is stored on the stack
+			m_context << eth::Instruction::SWAP1;
+		else
+			m_context << eth::Instruction::DUP2 << load;
+		// stack: <base_ref> <index> <length>
+		// check out-of-bounds access
+		m_context << eth::Instruction::DUP2 << eth::Instruction::LT << eth::Instruction::ISZERO;
+		// out-of-bounds access throws exception
+		m_context.appendConditionalJumpTo(m_context.errorTag());
+	}
+	else if (location == DataLocation::CallData && _arrayType.isDynamicallySized())
+		// remove length if present
+		m_context << eth::Instruction::SWAP1 << eth::Instruction::POP;
 
 	// stack: <base_ref> <index>
 	m_context << eth::Instruction::SWAP1;
@@ -671,18 +719,13 @@ void ArrayUtils::accessIndex(ArrayType const& _arrayType) const
 		if (!_arrayType.isByteArray())
 		{
 			m_context << eth::Instruction::SWAP1;
-			m_context << _arrayType.getBaseType()->getCalldataEncodedSize() << eth::Instruction::MUL;
+			if (location == DataLocation::CallData)
+				m_context << _arrayType.getBaseType()->getCalldataEncodedSize();
+			else
+				m_context << u256(_arrayType.memoryHeadSize());
+			m_context << eth::Instruction::MUL;
 		}
 		m_context << eth::Instruction::ADD;
-		//@todo we should also load if it is a reference type of dynamic length
-		// but we should apply special logic if we load from calldata.
-		if (_arrayType.getBaseType()->isValueType())
-			CompilerUtils(m_context).loadFromMemoryDynamic(
-				*_arrayType.getBaseType(),
-				location == DataLocation::CallData,
-				!_arrayType.isByteArray(),
-				false
-			);
 		break;
 	case DataLocation::Storage:
 		m_context << eth::Instruction::SWAP1;
diff --git a/libsolidity/ArrayUtils.h b/libsolidity/ArrayUtils.h
index 8d56f3c8f..c047fdcc0 100644
--- a/libsolidity/ArrayUtils.h
+++ b/libsolidity/ArrayUtils.h
@@ -44,7 +44,11 @@ public:
 	/// Stack pre: source_reference [source_byte_offset/source_length] target_reference target_byte_offset
 	/// Stack post: target_reference target_byte_offset
 	void copyArrayToStorage(ArrayType const& _targetType, ArrayType const& _sourceType) const;
-	/// Copies an array (which cannot be dynamically nested) from anywhere to memory.
+	/// Copies the data part of an array (which cannot be dynamically nested) from anywhere
+	/// to a given position in memory.
+	/// This always copies contained data as is (i.e. structs and fixed-size arrays are copied in
+	/// place as required by the ABI encoding). Use CompilerUtils::convertType if you want real
+	/// memory copies of nested arrays.
 	/// Stack pre: memory_offset source_item
 	/// Stack post: memory_offest + length(padded)
 	void copyArrayToMemory(ArrayType const& _sourceType, bool _padToWordBoundaries = true) const;
@@ -74,12 +78,11 @@ public:
 	/// Stack pre: reference (excludes byte offset for dynamic storage arrays)
 	/// Stack post: reference length
 	void retrieveLength(ArrayType const& _arrayType) const;
-	/// Retrieves the value at a specific index. If the location is storage, only retrieves the
-	/// position.
+	/// Performs bounds checking and returns a reference on the stack.
 	/// Stack pre: reference [length] index
-	/// Stack post for storage: slot byte_offset
-	/// Stack post for calldata: value
-	void accessIndex(ArrayType const& _arrayType) const;
+	/// Stack post (storage): storage_slot byte_offset
+	/// Stack post: memory/calldata_offset
+	void accessIndex(ArrayType const& _arrayType, bool _doBoundsCheck = true) const;
 
 private:
 	/// Adds the given number of bytes to a storage byte offset counter and also increments
diff --git a/libsolidity/Compiler.cpp b/libsolidity/Compiler.cpp
index b05a7a9b1..6ed6480f2 100644
--- a/libsolidity/Compiler.cpp
+++ b/libsolidity/Compiler.cpp
@@ -261,7 +261,7 @@ void Compiler::appendCalldataUnpacker(
 {
 	// We do not check the calldata size, everything is zero-paddedd
 
-	//@todo this does not yet support nested arrays
+	//@todo this does not yet support nested dynamic arrays
 
 	if (_startOffset == u256(-1))
 		_startOffset = u256(CompilerUtils::dataStartOffset);
@@ -279,6 +279,12 @@ void Compiler::appendCalldataUnpacker(
 			solAssert(!arrayType.getBaseType()->isDynamicallySized(), "Nested arrays not yet implemented.");
 			if (_fromMemory)
 			{
+				solAssert(
+					arrayType.getBaseType()->isValueType(),
+					"Nested memory arrays not yet implemented here."
+				);
+				// @todo If base type is an array or struct, it is still calldata-style encoded, so
+				// we would have to convert it like below.
 				solAssert(arrayType.location() == DataLocation::Memory, "");
 				// compute data pointer
 				m_context << eth::Instruction::DUP1 << eth::Instruction::MLOAD;
@@ -311,6 +317,7 @@ void Compiler::appendCalldataUnpacker(
 				}
 				if (arrayType.location() == DataLocation::Memory)
 				{
+					// stack: calldata_ref [length] next_calldata
 					// copy to memory
 					// move calldata type up again
 					CompilerUtils(m_context).moveIntoStack(calldataType->getSizeOnStack());
@@ -657,7 +664,7 @@ void Compiler::appendStackVariableInitialisation(VariableDeclaration const& _var
 {
 	CompilerContext::LocationSetter location(m_context, _variable);
 	m_context.addVariable(_variable);
-	ExpressionCompiler(m_context).appendStackVariableInitialisation(*_variable.getType());
+	CompilerUtils(m_context).pushZeroValue(*_variable.getType());
 }
 
 void Compiler::compileExpression(Expression const& _expression, TypePointer const& _targetType)
diff --git a/libsolidity/CompilerUtils.cpp b/libsolidity/CompilerUtils.cpp
index 47a9a3542..208d7cecc 100644
--- a/libsolidity/CompilerUtils.cpp
+++ b/libsolidity/CompilerUtils.cpp
@@ -54,6 +54,13 @@ void CompilerUtils::storeFreeMemoryPointer()
 	m_context << u256(freeMemoryPointer) << eth::Instruction::MSTORE;
 }
 
+void CompilerUtils::allocateMemory()
+{
+	fetchFreeMemoryPointer();
+	m_context << eth::Instruction::SWAP1 << eth::Instruction::DUP2 << eth::Instruction::ADD;
+	storeFreeMemoryPointer();
+}
+
 void CompilerUtils::toSizeAfterFreeMemoryPointer()
 {
 	fetchFreeMemoryPointer();
@@ -101,17 +108,20 @@ void CompilerUtils::storeInMemory(unsigned _offset)
 
 void CompilerUtils::storeInMemoryDynamic(Type const& _type, bool _padToWordBoundaries)
 {
-	if (_type.getCategory() == Type::Category::Array)
-		ArrayUtils(m_context).copyArrayToMemory(
-			dynamic_cast<ArrayType const&>(_type),
-			_padToWordBoundaries
-		);
+	if (auto ref = dynamic_cast<ReferenceType const*>(&_type))
+	{
+		solAssert(ref->location() == DataLocation::Memory, "");
+		storeInMemoryDynamic(IntegerType(256), _padToWordBoundaries);
+	}
 	else
 	{
 		unsigned numBytes = prepareMemoryStore(_type, _padToWordBoundaries);
 		if (numBytes > 0)
 		{
-			solAssert(_type.getSizeOnStack() == 1, "Memory store of types with stack size != 1 not implemented.");
+			solAssert(
+				_type.getSizeOnStack() == 1,
+				"Memory store of types with stack size != 1 not implemented."
+			);
 			m_context << eth::Instruction::DUP2 << eth::Instruction::MSTORE;
 			m_context << u256(numBytes) << eth::Instruction::ADD;
 		}
@@ -164,7 +174,10 @@ void CompilerUtils::encodeToMemory(
 				type = _givenTypes[i]; // delay conversion
 			else
 				convertType(*_givenTypes[i], *targetType, true);
-			storeInMemoryDynamic(*type, _padToWordBoundaries);
+			if (auto arrayType = dynamic_cast<ArrayType const*>(type.get()))
+				ArrayUtils(m_context).copyArrayToMemory(*arrayType, _padToWordBoundaries);
+			else
+				storeInMemoryDynamic(*type, _padToWordBoundaries);
 		}
 		stackPos += _givenTypes[i]->getSizeOnStack();
 	}
@@ -207,7 +220,7 @@ void CompilerUtils::encodeToMemory(
 			m_context << eth::swapInstruction(arrayType.getSizeOnStack() + 1) << eth::Instruction::POP;
 			// stack: ... <end_of_mem''> <value...>
 			// copy data part
-			storeInMemoryDynamic(arrayType, true);
+			ArrayUtils(m_context).copyArrayToMemory(arrayType, _padToWordBoundaries);
 			// stack: ... <end_of_mem'''>
 
 			thisDynPointer++;
@@ -349,63 +362,64 @@ void CompilerUtils::convertType(Type const& _typeOnStack, Type const& _targetTyp
 			{
 				// stack: <source ref> (variably sized)
 				unsigned stackSize = typeOnStack.getSizeOnStack();
-				fetchFreeMemoryPointer();
-				moveIntoStack(stackSize);
-				// stack: <mem start> <source ref> (variably sized)
-				if (targetType.isDynamicallySized())
+				bool fromStorage = (typeOnStack.location() == DataLocation::Storage);
+				if (fromStorage)
 				{
-					bool fromStorage = (typeOnStack.location() == DataLocation::Storage);
-					// store length
-					if (fromStorage)
-					{
-						stackSize--;
-						// remove storage offset, as requested by ArrayUtils::retrieveLength
-						m_context << eth::Instruction::POP;
-					}
-					ArrayUtils(m_context).retrieveLength(typeOnStack);
-					// Stack: <mem start> <source ref> <length>
-					m_context << eth::dupInstruction(2 + stackSize) << eth::Instruction::MSTORE;
-					m_context << eth::dupInstruction(1 + stackSize) << u256(0x20);
-					m_context << eth::Instruction::ADD;
-					moveIntoStack(stackSize);
-					if (fromStorage)
-					{
-						m_context << u256(0);
-						stackSize++;
-					}
+					stackSize--;
+					// remove storage offset, as requested by ArrayUtils::retrieveLength
+					m_context << eth::Instruction::POP;
 				}
-				else
+				ArrayUtils(m_context).retrieveLength(typeOnStack);
+
+				// allocate memory
+				// stack: <source ref> (variably sized) <length>
+				m_context << eth::Instruction::DUP1;
+				ArrayUtils(m_context).convertLengthToSize(targetType, true);
+				// stack: <source ref> (variably sized) <length> <size>
+				if (targetType.isDynamicallySized())
+					m_context << u256(0x20) << eth::Instruction::ADD;
+				allocateMemory();
+				// stack: <source ref> (variably sized) <length> <mem start>
+				m_context << eth::Instruction::DUP1;
+				moveIntoStack(2 + stackSize);
+				if (targetType.isDynamicallySized())
 				{
-					m_context << eth::dupInstruction(1 + stackSize);
-					moveIntoStack(stackSize);
+					m_context << eth::Instruction::DUP2;
+					storeInMemoryDynamic(IntegerType(256));
 				}
-				// Stack: <mem start> <mem data start> <value>
-				// Store data part.
-				storeInMemoryDynamic(typeOnStack);
-				// Stack <mem start> <mem end>
-				storeFreeMemoryPointer();
-			}
-			else if (typeOnStack.location() == DataLocation::CallData)
-			{
-				// Stack: <offset> [<length>]
-				// length is present if dynamically sized
-				fetchFreeMemoryPointer();
-				moveIntoStack(typeOnStack.getSizeOnStack());
-				// stack: memptr calldataoffset [<length>]
-				if (typeOnStack.isDynamicallySized())
+				// stack: <mem start> <source ref> (variably sized) <length> <mem data pos>
+				if (targetType.getBaseType()->isValueType())
 				{
-					solAssert(targetType.isDynamicallySized(), "");
-					m_context << eth::Instruction::DUP3 << eth::Instruction::DUP2;
-					storeInMemoryDynamic(IntegerType(256));
-					moveIntoStack(typeOnStack.getSizeOnStack());
+					solAssert(typeOnStack.getBaseType()->isValueType(), "");
+					copyToStackTop(2 + stackSize, stackSize);
+					if (fromStorage)
+						m_context << u256(0); // add byte offset again
+					ArrayUtils(m_context).copyArrayToMemory(typeOnStack);
 				}
 				else
-					m_context << eth::Instruction::DUP2 << eth::Instruction::SWAP1;
-				// stack: mem_ptr mem_data_ptr calldataoffset [<length>]
-				storeInMemoryDynamic(typeOnStack);
-				storeFreeMemoryPointer();
+				{
+					m_context << u256(0) << eth::Instruction::SWAP1;
+					// stack: <mem start> <source ref> (variably sized) <length> <counter> <mem data pos>
+					auto repeat = m_context.newTag();
+					m_context << repeat;
+					m_context << eth::Instruction::DUP3 << eth::Instruction::DUP3;
+					m_context << eth::Instruction::LT << eth::Instruction::ISZERO;
+					auto loopEnd = m_context.appendConditionalJump();
+					copyToStackTop(3 + stackSize, stackSize);
+					copyToStackTop(2 + stackSize, 1);
+					ArrayUtils(m_context).accessIndex(typeOnStack, false);
+					convertType(*typeOnStack.getBaseType(), *targetType.getBaseType(), _cleanupNeeded);
+					storeInMemoryDynamic(*targetType.getBaseType(), true);
+					m_context << eth::Instruction::SWAP1 << u256(1) << eth::Instruction::ADD;
+					m_context << eth::Instruction::SWAP1;
+					m_context.appendJumpTo(repeat);
+					m_context << loopEnd;
+					m_context << eth::Instruction::POP;
+				}
+				// stack: <mem start> <source ref> (variably sized) <length> <mem data pos updated>
+				popStackSlots(2 + stackSize);
+				// Stack: <mem start>
 			}
-			// nothing to do for memory to memory
 			break;
 		}
 		default:
@@ -444,6 +458,57 @@ void CompilerUtils::convertType(Type const& _typeOnStack, Type const& _targetTyp
 	}
 }
 
+void CompilerUtils::pushZeroValue(const Type& _type)
+{
+	auto const* referenceType = dynamic_cast<ReferenceType const*>(&_type);
+	if (!referenceType || referenceType->location() == DataLocation::Storage)
+	{
+		for (size_t i = 0; i < _type.getSizeOnStack(); ++i)
+			m_context << u256(0);
+		return;
+	}
+	solAssert(referenceType->location() == DataLocation::Memory, "");
+
+	m_context << u256(max(32u, _type.getCalldataEncodedSize()));
+	allocateMemory();
+	m_context << eth::Instruction::DUP1;
+
+	if (auto structType = dynamic_cast<StructType const*>(&_type))
+		for (auto const& member: structType->getMembers())
+		{
+			pushZeroValue(*member.type);
+			storeInMemoryDynamic(*member.type);
+		}
+	else if (auto arrayType = dynamic_cast<ArrayType const*>(&_type))
+	{
+		if (arrayType->isDynamicallySized())
+		{
+			// zero length
+			m_context << u256(0);
+			storeInMemoryDynamic(IntegerType(256));
+		}
+		else if (arrayType->getLength() > 0)
+		{
+			m_context << arrayType->getLength() << eth::Instruction::SWAP1;
+			// stack: items_to_do memory_pos
+			auto repeat = m_context.newTag();
+			m_context << repeat;
+			pushZeroValue(*arrayType->getBaseType());
+			storeInMemoryDynamic(*arrayType->getBaseType());
+			m_context << eth::Instruction::SWAP1 << u256(1) << eth::Instruction::SWAP1;
+			m_context << eth::Instruction::SUB << eth::Instruction::SWAP1;
+			m_context << eth::Instruction::DUP2;
+			m_context.appendConditionalJumpTo(repeat);
+			m_context << eth::Instruction::SWAP1 << eth::Instruction::POP;
+		}
+	}
+	else
+		solAssert(false, "Requested initialisation for unknown type: " + _type.toString());
+
+	// remove the updated memory pointer
+	m_context << eth::Instruction::POP;
+}
+
 void CompilerUtils::moveToStackVariable(VariableDeclaration const& _variable)
 {
 	unsigned const stackPosition = m_context.baseToCurrentStackOffset(m_context.getBaseStackOffsetOfVariable(_variable));
diff --git a/libsolidity/CompilerUtils.h b/libsolidity/CompilerUtils.h
index a9e07f74f..7dd44da8f 100644
--- a/libsolidity/CompilerUtils.h
+++ b/libsolidity/CompilerUtils.h
@@ -41,6 +41,10 @@ public:
 	void fetchFreeMemoryPointer();
 	/// Stores the free memory pointer from the stack.
 	void storeFreeMemoryPointer();
+	/// Allocates a number of bytes in memory as given on the stack.
+	/// Stack pre: <size>
+	/// Stack post: <mem_start>
+	void allocateMemory();
 	/// Appends code that transforms memptr to (memptr - free_memptr) memptr
 	void toSizeAfterFreeMemoryPointer();
 
@@ -70,7 +74,8 @@ public:
 	/// @param _type type of the data on the stack
 	void storeInMemory(unsigned _offset);
 	/// Dynamic version of @see storeInMemory, expects the memory offset below the value on the stack
-	/// and also updates that. For arrays, only copies the data part.
+	/// and also updates that. For reference types, only copies the data pointer. Fails for
+	/// non-memory-references.
 	/// @param _padToWordBoundaries if true, adds zeros to pad to multiple of 32 bytes. Array elements
 	/// are always padded (except for byte arrays), regardless of this parameter.
 	/// Stack pre: memory_offset value...
@@ -107,6 +112,10 @@ public:
 	/// necessary.
 	void convertType(Type const& _typeOnStack, Type const& _targetType, bool _cleanupNeeded = false);
 
+	/// Creates a zero-value for the given type and puts it onto the stack. This might allocate
+	/// memory for memory references.
+	void pushZeroValue(Type const& _type);
+
 	/// Moves the value that is at the top of the stack to a stack variable.
 	void moveToStackVariable(VariableDeclaration const& _variable);
 	/// Copies an item that occupies @a _itemSize stack slots from a stack depth of @a _stackDepth
diff --git a/libsolidity/ExpressionCompiler.cpp b/libsolidity/ExpressionCompiler.cpp
index fb10eb83b..7ddcc0318 100644
--- a/libsolidity/ExpressionCompiler.cpp
+++ b/libsolidity/ExpressionCompiler.cpp
@@ -56,62 +56,6 @@ void ExpressionCompiler::appendStateVariableInitialization(VariableDeclaration c
 	StorageItem(m_context, _varDecl).storeValue(*_varDecl.getType(), _varDecl.getLocation(), true);
 }
 
-void ExpressionCompiler::appendStackVariableInitialisation(Type const& _type, bool _toMemory)
-{
-	CompilerUtils utils(m_context);
-	auto const* referenceType = dynamic_cast<ReferenceType const*>(&_type);
-	if (!referenceType || referenceType->location() == DataLocation::Storage)
-	{
-		for (size_t i = 0; i < _type.getSizeOnStack(); ++i)
-			m_context << u256(0);
-		if (_toMemory)
-			utils.storeInMemoryDynamic(_type);
-		return;
-	}
-	solAssert(referenceType->location() == DataLocation::Memory, "");
-	if (!_toMemory)
-	{
-		// allocate memory
-		utils.fetchFreeMemoryPointer();
-		m_context << eth::Instruction::DUP1 << u256(max(32u, _type.getCalldataEncodedSize()));
-		m_context << eth::Instruction::ADD;
-		utils.storeFreeMemoryPointer();
-		m_context << eth::Instruction::DUP1;
-	}
-
-	if (auto structType = dynamic_cast<StructType const*>(&_type))
-		for (auto const& member: structType->getMembers())
-			appendStackVariableInitialisation(*member.type, true);
-	else if (auto arrayType = dynamic_cast<ArrayType const*>(&_type))
-	{
-		if (arrayType->isDynamicallySized())
-		{
-			// zero length
-			m_context << u256(0);
-			CompilerUtils(m_context).storeInMemoryDynamic(IntegerType(256));
-		}
-		else if (arrayType->getLength() > 0)
-		{
-			m_context << arrayType->getLength() << eth::Instruction::SWAP1;
-			// stack: items_to_do memory_pos
-			auto repeat = m_context.newTag();
-			m_context << repeat;
-			appendStackVariableInitialisation(*arrayType->getBaseType(), true);
-			m_context << eth::Instruction::SWAP1 << u256(1) << eth::Instruction::SWAP1;
-			m_context << eth::Instruction::SUB << eth::Instruction::SWAP1;
-			m_context << eth::Instruction::DUP2;
-			m_context.appendConditionalJumpTo(repeat);
-			m_context << eth::Instruction::SWAP1 << eth::Instruction::POP;
-		}
-	}
-	else
-		solAssert(false, "Requested initialisation for unknown type: " + _type.toString());
-
-	if (!_toMemory)
-		// remove the updated memory pointer
-		m_context << eth::Instruction::POP;
-}
-
 void ExpressionCompiler::appendStateVariableAccessor(VariableDeclaration const& _varDecl)
 {
 	CompilerContext::LocationSetter locationSetter(m_context, _varDecl);
@@ -211,6 +155,8 @@ bool ExpressionCompiler::visit(Assignment const& _assignment)
 	TypePointer type = _assignment.getRightHandSide().getType();
 	if (!_assignment.getType()->dataStoredIn(DataLocation::Storage))
 	{
+		//@todo we should delay conversion here if RHS is not in memory, LHS is a MemoryItem
+		// and not dynamically-sized.
 		utils().convertType(*type, *_assignment.getType());
 		type = _assignment.getType();
 	}
@@ -827,8 +773,9 @@ bool ExpressionCompiler::visit(IndexAccess const& _indexAccess)
 		_indexAccess.getIndexExpression()->accept(*this);
 		// stack layout: <base_ref> [<length>] <index>
 		ArrayUtils(m_context).accessIndex(arrayType);
-		if (arrayType.location() == DataLocation::Storage)
+		switch (arrayType.location())
 		{
+		case DataLocation::Storage:
 			if (arrayType.isByteArray())
 			{
 				solAssert(!arrayType.isString(), "Index access to string is not allowed.");
@@ -836,6 +783,21 @@ bool ExpressionCompiler::visit(IndexAccess const& _indexAccess)
 			}
 			else
 				setLValueToStorageItem(_indexAccess);
+			break;
+		case DataLocation::Memory:
+			setLValue<MemoryItem>(_indexAccess, *_indexAccess.getType(), !arrayType.isByteArray());
+			break;
+		case DataLocation::CallData:
+			//@todo if we implement this, the value in calldata has to be added to the base offset
+			solAssert(!arrayType.getBaseType()->isDynamicallySized(), "Nested arrays not yet implemented.");
+			if (arrayType.getBaseType()->isValueType())
+				CompilerUtils(m_context).loadFromMemoryDynamic(
+					*arrayType.getBaseType(),
+					true,
+					!arrayType.isByteArray(),
+					false
+				);
+			break;
 		}
 	}
 	else
diff --git a/libsolidity/ExpressionCompiler.h b/libsolidity/ExpressionCompiler.h
index 747e241ef..642560c64 100644
--- a/libsolidity/ExpressionCompiler.h
+++ b/libsolidity/ExpressionCompiler.h
@@ -64,13 +64,6 @@ public:
 	/// Appends code to set a state variable to its initial value/expression.
 	void appendStateVariableInitialization(VariableDeclaration const& _varDecl);
 
-	/// Appends code to initialise a local variable.
-	/// If @a _toMemory is false, leaves the value on the stack. For memory references, this
-	/// allocates new memory.
-	/// If @a _toMemory is true, directly stores the data in the memory pos on the stack and
-	/// updates it.
-	void appendStackVariableInitialisation(Type const& _type, bool _toMemory = false);
-
 	/// Appends code for a State Variable accessor function
 	void appendStateVariableAccessor(VariableDeclaration const& _varDecl);
 
diff --git a/libsolidity/LValue.cpp b/libsolidity/LValue.cpp
index 1acf0a3e8..cf640e910 100644
--- a/libsolidity/LValue.cpp
+++ b/libsolidity/LValue.cpp
@@ -82,6 +82,62 @@ void StackVariable::setToZero(SourceLocation const& _location, bool) const
 			<< eth::Instruction::POP;
 }
 
+MemoryItem::MemoryItem(CompilerContext& _compilerContext, Type const& _type, bool _padded):
+	LValue(_compilerContext, _type),
+	m_padded(_padded)
+{
+}
+
+void MemoryItem::retrieveValue(SourceLocation const&, bool _remove) const
+{
+	if (m_dataType.isValueType())
+	{
+		if (!_remove)
+			m_context << eth::Instruction::DUP1;
+		CompilerUtils(m_context).loadFromMemoryDynamic(m_dataType, false, m_padded, false);
+	}
+	else
+		m_context << eth::Instruction::MLOAD;
+}
+
+void MemoryItem::storeValue(Type const& _sourceType, SourceLocation const&, bool _move) const
+{
+	CompilerUtils utils(m_context);
+	if (m_dataType.isValueType())
+	{
+		solAssert(_sourceType.isValueType(), "");
+		utils.moveIntoStack(_sourceType.getSizeOnStack());
+		utils.convertType(_sourceType, m_dataType, true);
+		if (!_move)
+		{
+			utils.moveToStackTop(m_dataType.getSizeOnStack());
+			utils.copyToStackTop(2, m_dataType.getSizeOnStack());
+		}
+		utils.storeInMemoryDynamic(m_dataType, m_padded);
+		m_context << eth::Instruction::POP;
+	}
+	else
+	{
+		solAssert(_sourceType == m_dataType, "Conversion not implemented for assignment to memory.");
+
+		solAssert(m_dataType.getSizeOnStack() == 1, "");
+		if (!_move)
+			m_context << eth::Instruction::DUP2 << eth::Instruction::SWAP1;
+		// stack: [value] value lvalue
+		// only store the reference
+		m_context << eth::Instruction::MSTORE;
+	}
+}
+
+void MemoryItem::setToZero(SourceLocation const&, bool _removeReference) const
+{
+	CompilerUtils utils(m_context);
+	if (!_removeReference)
+		m_context << eth::Instruction::DUP1;
+	utils.pushZeroValue(m_dataType);
+	utils.storeInMemoryDynamic(m_dataType, m_padded);
+	m_context << eth::Instruction::POP;
+}
 
 StorageItem::StorageItem(CompilerContext& _compilerContext, Declaration const& _declaration):
 	StorageItem(_compilerContext, *_declaration.getType())
diff --git a/libsolidity/LValue.h b/libsolidity/LValue.h
index 726d63328..882b3626e 100644
--- a/libsolidity/LValue.h
+++ b/libsolidity/LValue.h
@@ -97,6 +97,29 @@ private:
 	unsigned m_size;
 };
 
+/**
+ * Reference to some item in memory.
+ */
+class MemoryItem: public LValue
+{
+public:
+	MemoryItem(CompilerContext& _compilerContext, Type const& _type, bool _padded);
+	virtual unsigned sizeOnStack() const override { return 1; }
+	virtual void retrieveValue(SourceLocation const& _location, bool _remove = false) const override;
+	virtual void storeValue(
+		Type const& _sourceType,
+		SourceLocation const& _location = SourceLocation(),
+		bool _move = false
+	) const override;
+	virtual void setToZero(
+		SourceLocation const& _location = SourceLocation(),
+		bool _removeReference = true
+	) const override;
+private:
+	/// Special flag to deal with byte array elements.
+	bool m_padded = false;
+};
+
 /**
  * Reference to some item in storage. On the stack this is <storage key> <offset_inside_value>,
  * where 0 <= offset_inside_value < 32 and an offset of i means that the value is multiplied
diff --git a/libsolidity/Types.cpp b/libsolidity/Types.cpp
index 01876b5a7..15c367421 100644
--- a/libsolidity/Types.cpp
+++ b/libsolidity/Types.cpp
@@ -827,15 +827,16 @@ TypePointer ArrayType::externalType() const
 {
 	if (m_arrayKind != ArrayKind::Ordinary)
 		return this->copyForLocation(DataLocation::Memory, true);
-	if (!m_baseType->externalType())
+	TypePointer baseExt = m_baseType->externalType();
+	if (!baseExt)
 		return TypePointer();
 	if (m_baseType->getCategory() == Category::Array && m_baseType->isDynamicallySized())
 		return TypePointer();
 
 	if (isDynamicallySized())
-		return std::make_shared<ArrayType>(DataLocation::Memory, m_baseType->externalType());
+		return std::make_shared<ArrayType>(DataLocation::Memory, baseExt);
 	else
-		return std::make_shared<ArrayType>(DataLocation::Memory, m_baseType->externalType(), m_length);
+		return std::make_shared<ArrayType>(DataLocation::Memory, baseExt, m_length);
 }
 
 TypePointer ArrayType::copyForLocation(DataLocation _location, bool _isPointer) const
@@ -1268,15 +1269,17 @@ FunctionTypePointer FunctionType::externalFunctionType() const
 
 	for (auto type: m_parameterTypes)
 	{
-		if (!type->externalType())
+		if (auto ext = type->externalType())
+			paramTypes.push_back(ext);
+		else
 			return FunctionTypePointer();
-		paramTypes.push_back(type->externalType());
 	}
 	for (auto type: m_returnParameterTypes)
 	{
-		if (!type->externalType())
+		if (auto ext = type->externalType())
+			retParamTypes.push_back(ext);
+		else
 			return FunctionTypePointer();
-		retParamTypes.push_back(type->externalType());
 	}
 	return make_shared<FunctionType>(paramTypes, retParamTypes, m_parameterNames, m_returnParameterNames, m_location, m_arbitraryParameters);
 }
diff --git a/libsolidity/Types.h b/libsolidity/Types.h
index 9d412cd68..9d9aaaba7 100644
--- a/libsolidity/Types.h
+++ b/libsolidity/Types.h
@@ -179,6 +179,9 @@ public:
 	/// is not a simple big-endian encoding or the type cannot be stored in calldata.
 	/// If @a _padded then it is assumed that each element is padded to a multiple of 32 bytes.
 	virtual unsigned getCalldataEncodedSize(bool _padded) const { (void)_padded; return 0; }
+	/// @returns the size of this data type in bytes when stored in memory. For memory-reference
+	/// types, this is the size of the memory pointer.
+	virtual unsigned memoryHeadSize() const { return getCalldataEncodedSize(); }
 	/// Convenience version of @see getCalldataEncodedSize(bool)
 	unsigned getCalldataEncodedSize() const { return getCalldataEncodedSize(true); }
 	/// @returns true if the type is dynamically encoded in calldata
@@ -373,6 +376,8 @@ public:
 	explicit ReferenceType(DataLocation _location): m_location(_location) {}
 	DataLocation location() const { return m_location; }
 
+	virtual unsigned memoryHeadSize() const override { return 32; }
+
 	/// @returns a copy of this type with location (recursively) changed to @a _location,
 	/// whereas isPointer is only shallowly changed - the deep copy is always a bound reference.
 	virtual TypePointer copyForLocation(DataLocation _location, bool _isPointer) const = 0;
diff --git a/mix/DebuggingStateWrapper.cpp b/mix/DebuggingStateWrapper.cpp
index b8fbdef30..42c429224 100644
--- a/mix/DebuggingStateWrapper.cpp
+++ b/mix/DebuggingStateWrapper.cpp
@@ -38,13 +38,17 @@ using namespace dev::mix;
 
 namespace
 {
-	static QVariantList memDumpToList(bytes const& _bytes, unsigned _width)
+	static QVariantList memDumpToList(bytes const& _bytes, unsigned _width, bool _includeAddress = false)
 	{
 		QVariantList dumpList;
 		for (unsigned i = 0; i < _bytes.size(); i += _width)
 		{
 			std::stringstream ret;
-
+			if (_includeAddress)
+			{
+				ret << std::setfill('0') << std::setw(6) << std::hex << i << " ";
+				ret << "   ";
+			}
 			for (unsigned j = i; j < i + _width; ++j)
 				if (j < _bytes.size())
 					if (_bytes[j] >= 32 && _bytes[j] < 127)
@@ -137,7 +141,7 @@ QStringList QMachineState::debugStorage()
 
 QVariantList QMachineState::debugMemory()
 {
-	return memDumpToList(m_state.memory, 16);
+	return memDumpToList(m_state.memory, 16, true);
 }
 
 QCallData* QMachineState::getDebugCallData(QObject* _owner, bytes const& _data)
diff --git a/test/libsolidity/SolidityEndToEndTest.cpp b/test/libsolidity/SolidityEndToEndTest.cpp
index 75793abf7..a01e98cf8 100644
--- a/test/libsolidity/SolidityEndToEndTest.cpp
+++ b/test/libsolidity/SolidityEndToEndTest.cpp
@@ -4691,6 +4691,53 @@ BOOST_AUTO_TEST_CASE(memory_types_initialisation)
 	BOOST_CHECK(callContractFunction("nestedStat()") == encodeArgs(vector<u256>(3 * 7)));
 }
 
+BOOST_AUTO_TEST_CASE(memory_arrays_index_access_write)
+{
+	char const* sourceCode = R"(
+		contract Test {
+			function set(uint24[3][4] x) {
+				x[2][2] = 1;
+				x[3][2] = 7;
+			}
+			function f() returns (uint24[3][4]){
+				uint24[3][4] memory data;
+				set(data);
+				return data;
+			}
+		}
+	)";
+	compileAndRun(sourceCode, 0, "Test");
+
+	vector<u256> data(3 * 4);
+	data[3 * 2 + 2] = 1;
+	data[3 * 3 + 2] = 7;
+	BOOST_CHECK(callContractFunction("f()") == encodeArgs(data));
+}
+
+BOOST_AUTO_TEST_CASE(memory_arrays_dynamic_index_access_write)
+{
+	char const* sourceCode = R"(
+		contract Test {
+			uint24[3][][4] data;
+			function set(uint24[3][][4] x) internal returns (uint24[3][][4]) {
+				x[1][2][2] = 1;
+				x[1][3][2] = 7;
+				return x;
+			}
+			function f() returns (uint24[3][]) {
+				data[1].length = 4;
+				return set(data)[1];
+			}
+		}
+	)";
+	compileAndRun(sourceCode, 0, "Test");
+
+	vector<u256> data(3 * 4);
+	data[3 * 2 + 2] = 1;
+	data[3 * 3 + 2] = 7;
+	BOOST_CHECK(callContractFunction("f()") == encodeArgs(u256(0x20), u256(4), data));
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 
 }