diff --git a/eth/main.cpp b/eth/main.cpp
index 2f4f7b571..f0af271d0 100644
--- a/eth/main.cpp
+++ b/eth/main.cpp
@@ -598,7 +598,7 @@ int main(int argc, char** argv)
 					e.setup(&r);
 
 					if (format == "pretty")
-						e.go([&](uint64_t steps, Instruction instr, unsigned newMemSize, bigint gasCost, void* vvm, void const* vextVM)
+						e.go([&](uint64_t steps, Instruction instr, bigint newMemSize, bigint gasCost, void* vvm, void const* vextVM)
 						{
 							eth::VM* vm = (VM*)vvm;
 							eth::ExtVM const* ext = (ExtVM const*)vextVM;
@@ -612,14 +612,14 @@ int main(int argc, char** argv)
 							f << dec << ext->level << " | " << ext->myAddress << " | #" << steps << " | " << hex << setw(4) << setfill('0') << vm->curPC() << " : " << c_instructionInfo.at(instr).name << " | " << dec << vm->gas() << " | -" << dec << gasCost << " | " << newMemSize << "x32";
 						});
 					else if (format == "standard")
-						e.go([&](uint64_t, Instruction instr, unsigned, bigint, void* vvm, void const* vextVM)
+						e.go([&](uint64_t, Instruction instr, bigint, bigint, void* vvm, void const* vextVM)
 						{
 							eth::VM* vm = (VM*)vvm;
 							eth::ExtVM const* ext = (ExtVM const*)vextVM;
 							f << ext->myAddress << " " << hex << toHex(eth::toCompactBigEndian(vm->curPC(), 1)) << " " << hex << toHex(eth::toCompactBigEndian((int)(byte)instr, 1)) << " " << hex << toHex(eth::toCompactBigEndian((uint64_t)vm->gas(), 1)) << endl;
 						});
 					else if (format == "standard+")
-						e.go([&](uint64_t, Instruction instr, unsigned, bigint, void* vvm, void const* vextVM)
+						e.go([&](uint64_t, Instruction instr, bigint, bigint, void* vvm, void const* vextVM)
 						{
 							eth::VM* vm = (VM*)vvm;
 							eth::ExtVM const* ext = (ExtVM const*)vextVM;
diff --git a/libethereum/Executive.cpp b/libethereum/Executive.cpp
index 9096b5d64..6562a0cf8 100644
--- a/libethereum/Executive.cpp
+++ b/libethereum/Executive.cpp
@@ -144,7 +144,7 @@ bool Executive::create(Address _sender, u256 _endowment, u256 _gasPrice, u256 _g
 
 OnOpFunc Executive::simpleTrace()
 {
-	return [](uint64_t steps, Instruction inst, unsigned newMemSize, bigint gasCost, void* voidVM, void const* voidExt)
+	return [](uint64_t steps, Instruction inst, bigint newMemSize, bigint gasCost, void* voidVM, void const* voidExt)
 	{
 		ExtVM const& ext = *(ExtVM const*)voidExt;
 		VM& vm = *(VM*)voidVM;
diff --git a/libevm/ExtVMFace.h b/libevm/ExtVMFace.h
index 4890a5979..e53d90734 100644
--- a/libevm/ExtVMFace.h
+++ b/libevm/ExtVMFace.h
@@ -83,6 +83,6 @@ public:
 	std::set<Address> suicides;	///< Any accounts that have suicided.
 };
 
-typedef std::function<void(uint64_t /*steps*/, Instruction /*instr*/, unsigned /*newMemSize*/, bigint /*gasCost*/, void/*VM*/*, void/*ExtVM*/ const*)> OnOpFunc;
+typedef std::function<void(uint64_t /*steps*/, Instruction /*instr*/, bigint /*newMemSize*/, bigint /*gasCost*/, void/*VM*/*, void/*ExtVM*/ const*)> OnOpFunc;
 
 }
diff --git a/libevm/VM.h b/libevm/VM.h
index df89c0b42..7a3c6f6e1 100644
--- a/libevm/VM.h
+++ b/libevm/VM.h
@@ -98,7 +98,7 @@ template <class Ext> eth::bytesConstRef eth::VM::go(Ext& _ext, OnOpFunc const& _
 
 		// FEES...
 		bigint runGas = c_stepGas;
-		unsigned newTempSize = (unsigned)m_temp.size();
+		bigint newTempSize = m_temp.size();
 		switch (inst)
 		{
 		case Instruction::STOP:
@@ -126,32 +126,32 @@ template <class Ext> eth::bytesConstRef eth::VM::go(Ext& _ext, OnOpFunc const& _
 		// These all operate on memory and therefore potentially expand it:
 		case Instruction::MSTORE:
 			require(2);
-			newTempSize = (unsigned)m_stack.back() + 32;
+			newTempSize = m_stack.back() + 32;
 			break;
 		case Instruction::MSTORE8:
 			require(2);
-			newTempSize = (unsigned)m_stack.back() + 1;
+			newTempSize = m_stack.back() + 1;
 			break;
 		case Instruction::MLOAD:
 			require(1);
-			newTempSize = (unsigned)m_stack.back() + 32;
+			newTempSize = m_stack.back() + 32;
 			break;
 		case Instruction::RETURN:
 			require(2);
-			newTempSize = (unsigned)m_stack.back() + (unsigned)m_stack[m_stack.size() - 2];
+			newTempSize = m_stack.back() + m_stack[m_stack.size() - 2];
 			break;
 		case Instruction::SHA3:
 			require(2);
 			runGas = c_sha3Gas;
-			newTempSize = (unsigned)m_stack.back() + (unsigned)m_stack[m_stack.size() - 2];
+			newTempSize = m_stack.back() + m_stack[m_stack.size() - 2];
 			break;
 		case Instruction::CALLDATACOPY:
 			require(3);
-			newTempSize = (unsigned)m_stack.back() + (unsigned)m_stack[m_stack.size() - 3];
+			newTempSize = m_stack.back() + m_stack[m_stack.size() - 3];
 			break;
 		case Instruction::CODECOPY:
 			require(3);
-			newTempSize = (unsigned)m_stack.back() + (unsigned)m_stack[m_stack.size() - 3];
+			newTempSize = m_stack.back() + m_stack[m_stack.size() - 3];
 			break;
 
 		case Instruction::BALANCE:
@@ -160,15 +160,15 @@ template <class Ext> eth::bytesConstRef eth::VM::go(Ext& _ext, OnOpFunc const& _
 
 		case Instruction::CALL:
 			require(7);
-			runGas = c_callGas + (unsigned)m_stack[m_stack.size() - 1];
-			newTempSize = std::max((unsigned)m_stack[m_stack.size() - 6] + (unsigned)m_stack[m_stack.size() - 7], (unsigned)m_stack[m_stack.size() - 4] + (unsigned)m_stack[m_stack.size() - 5]);
+			runGas = c_callGas + m_stack[m_stack.size() - 1];
+			newTempSize = std::max(m_stack[m_stack.size() - 6] + m_stack[m_stack.size() - 7], m_stack[m_stack.size() - 4] + m_stack[m_stack.size() - 5]);
 			break;
 
 		case Instruction::CREATE:
 		{
 			require(3);
-			unsigned inOff = (unsigned)m_stack[m_stack.size() - 2];
-			unsigned inSize = (unsigned)m_stack[m_stack.size() - 3];
+			auto inOff = m_stack[m_stack.size() - 2];
+			auto inSize = m_stack[m_stack.size() - 3];
 			newTempSize = inOff + inSize;
             runGas = c_createGas;
 			break;
@@ -183,7 +183,7 @@ template <class Ext> eth::bytesConstRef eth::VM::go(Ext& _ext, OnOpFunc const& _
 			runGas += c_memoryGas * (newTempSize - m_temp.size()) / 32;
 
 		if (_onOp)
-			_onOp(osteps - _steps - 1, inst, newTempSize > m_temp.size() ? (newTempSize - m_temp.size()) / 32 : 0, runGas, this, &_ext);
+			_onOp(osteps - _steps - 1, inst, newTempSize > m_temp.size() ? (newTempSize - m_temp.size()) / 32 : bigint(0), runGas, this, &_ext);
 
 		if (m_gas < runGas)
 		{
@@ -195,7 +195,7 @@ template <class Ext> eth::bytesConstRef eth::VM::go(Ext& _ext, OnOpFunc const& _
 		m_gas = (u256)((bigint)m_gas - runGas);
 
 		if (newTempSize > m_temp.size())
-			m_temp.resize(newTempSize);
+			m_temp.resize((size_t)newTempSize);
 
 		// EXECUTE...
 		switch (inst)
@@ -299,6 +299,18 @@ template <class Ext> eth::bytesConstRef eth::VM::go(Ext& _ext, OnOpFunc const& _
 			m_stack[m_stack.size() - 2] = m_stack.back() < 32 ? (m_stack[m_stack.size() - 2] >> (uint)(8 * (31 - m_stack.back()))) & 0xff : 0;
 			m_stack.pop_back();
 			break;
+		case Instruction::ADDMOD:
+			require(3);
+			m_stack[m_stack.size() - 3] = u256((bigint(m_stack.back()) + bigint(m_stack[m_stack.size() - 2])) % m_stack[m_stack.size() - 3]);
+			m_stack.pop_back();
+			m_stack.pop_back();
+			break;
+		case Instruction::MULMOD:
+			require(3);
+			m_stack[m_stack.size() - 3] = u256((bigint(m_stack.back()) * bigint(m_stack[m_stack.size() - 2])) % m_stack[m_stack.size() - 3]);
+			m_stack.pop_back();
+			m_stack.pop_back();
+			break;
 		case Instruction::SHA3:
 		{
 			require(2);
@@ -610,9 +622,6 @@ template <class Ext> eth::bytesConstRef eth::VM::go(Ext& _ext, OnOpFunc const& _
 		}
 		case Instruction::STOP:
 			return bytesConstRef();
-		case Instruction::NOP1:
-		case Instruction::NOP2:
-			break;
 		default:
 			throw BadInstruction();
 		}
diff --git a/libevmface/Instruction.cpp b/libevmface/Instruction.cpp
index 7f2f51c67..b42244c3e 100644
--- a/libevmface/Instruction.cpp
+++ b/libevmface/Instruction.cpp
@@ -47,6 +47,8 @@ const std::map<std::string, Instruction> eth::c_instructions =
 	{ "OR", Instruction::OR },
 	{ "XOR", Instruction::XOR },
 	{ "BYTE", Instruction::BYTE },
+	{ "ADDMOD", Instruction::ADDMOD },
+	{ "MULMOD", Instruction::MULMOD },
 	{ "SHA3", Instruction::SHA3 },
 	{ "ADDRESS", Instruction::ADDRESS },
 	{ "BALANCE", Instruction::BALANCE },
@@ -66,8 +68,6 @@ const std::map<std::string, Instruction> eth::c_instructions =
 	{ "DIFFICULTY", Instruction::DIFFICULTY },
 	{ "GASLIMIT", Instruction::GASLIMIT },
 	{ "POP", Instruction::POP },
-	{ "NOP1", Instruction::NOP1 },
-	{ "NOP2", Instruction::NOP2 },
 	{ "MLOAD", Instruction::MLOAD },
 	{ "MSTORE", Instruction::MSTORE },
 	{ "MSTORE8", Instruction::MSTORE8 },
@@ -170,6 +170,8 @@ const std::map<Instruction, InstructionInfo> eth::c_instructionInfo =
 	{ Instruction::OR,			{ "OR",				0, 2, 1 } },
 	{ Instruction::XOR,			{ "XOR",			0, 2, 1 } },
 	{ Instruction::BYTE,		{ "BYTE",			0, 2, 1 } },
+	{ Instruction::ADDMOD,		{ "ADDMOD",			0, 3, 1 } },
+	{ Instruction::MULMOD,		{ "MULMOD",			0, 3, 1 } },
 	{ Instruction::SHA3,		{ "SHA3",			0, 2, 1 } },
 	{ Instruction::ADDRESS,		{ "ADDRESS",		0, 0, 1 } },
 	{ Instruction::BALANCE,		{ "BALANCE",		0, 1, 1 } },
diff --git a/libevmface/Instruction.h b/libevmface/Instruction.h
index 03f2b9d7d..bf107a860 100644
--- a/libevmface/Instruction.h
+++ b/libevmface/Instruction.h
@@ -56,6 +56,8 @@ enum class Instruction: uint8_t
 	OR,
 	XOR,
 	BYTE,
+	ADDMOD,
+	MULMOD,
 
 	SHA3 = 0x20,
 
@@ -79,9 +81,7 @@ enum class Instruction: uint8_t
 	GASLIMIT,
 
 	POP = 0x50,
-	NOP1,
-	NOP2,
-	MLOAD,
+	MLOAD = 0x53,
 	MSTORE,
 	MSTORE8,
 	SLOAD,