diff --git a/libevmjit/Compiler.cpp b/libevmjit/Compiler.cpp
index 92a2b0e0c..d7240a415 100644
--- a/libevmjit/Compiler.cpp
+++ b/libevmjit/Compiler.cpp
@@ -721,8 +721,8 @@ void Compiler::compileBasicBlock(BasicBlock& _basicBlock, RuntimeManager& _runti
 
 		case Instruction::CALLDATALOAD:
 		{
-			auto index = stack.pop();
-			auto value = _ext.calldataload(index);
+			auto idx = stack.pop();
+			auto value = _ext.calldataload(idx);
 			stack.push(value);
 			break;
 		}
diff --git a/libevmjit/Ext.cpp b/libevmjit/Ext.cpp
index d35aebc68..9b1e0983b 100644
--- a/libevmjit/Ext.cpp
+++ b/libevmjit/Ext.cpp
@@ -45,7 +45,6 @@ std::array<FuncDesc, sizeOf<EnvFunc>::value> const& getEnvFuncDescs()
 		FuncDesc{"env_log", getFunctionType(Type::Void, {Type::EnvPtr, Type::BytePtr, Type::Size, Type::WordPtr, Type::WordPtr, Type::WordPtr, Type::WordPtr})},
 		FuncDesc{"env_blockhash", getFunctionType(Type::Void, {Type::EnvPtr, Type::WordPtr, Type::WordPtr})},
 		FuncDesc{"env_extcode", getFunctionType(Type::BytePtr, {Type::EnvPtr, Type::WordPtr, Type::Size->getPointerTo()})},
-		FuncDesc{"ext_calldataload", getFunctionType(Type::Void, {Type::RuntimeDataPtr, Type::WordPtr, Type::WordPtr})},
 	}};
 
 	return descs;
@@ -101,12 +100,26 @@ void Ext::sstore(llvm::Value* _index, llvm::Value* _value)
 	createCall(EnvFunc::sstore, {getRuntimeManager().getEnvPtr(), byPtr(_index), byPtr(_value)}); // Uses native endianness
 }
 
-llvm::Value* Ext::calldataload(llvm::Value* _index)
+llvm::Value* Ext::calldataload(llvm::Value* _idx)
 {
 	auto ret = getArgAlloca();
-	createCall(EnvFunc::calldataload, {getRuntimeManager().getDataPtr(), byPtr(_index), ret});
-	ret = m_builder.CreateLoad(ret);
-	return Endianness::toNative(m_builder, ret);
+	auto result = m_builder.CreateBitCast(ret, Type::BytePtr);
+
+	auto callDataSize = getRuntimeManager().getCallDataSize();
+	auto callDataSize64 = m_builder.CreateTrunc(callDataSize, Type::Size);
+	auto idxValid = m_builder.CreateICmpULT(_idx, callDataSize);
+	auto idx = m_builder.CreateTrunc(m_builder.CreateSelect(idxValid, _idx, callDataSize), Type::Size, "idx");
+
+	auto end = m_builder.CreateNUWAdd(idx, m_builder.getInt64(32));
+	end = m_builder.CreateSelect(m_builder.CreateICmpULE(end, callDataSize64), end, callDataSize64);
+	auto copySize = m_builder.CreateNUWSub(end, idx);
+	auto padSize = m_builder.CreateNUWSub(m_builder.getInt64(32), copySize);
+	auto dataBegin = m_builder.CreateGEP(Type::Byte, getRuntimeManager().getCallData(), idx);
+	m_builder.CreateMemCpy(result, dataBegin, copySize, 1);
+	auto pad = m_builder.CreateGEP(Type::Byte, result, copySize);
+	m_builder.CreateMemSet(pad, m_builder.getInt8(0), padSize, 1);
+
+	return Endianness::toNative(m_builder, m_builder.CreateLoad(ret));
 }
 
 llvm::Value* Ext::balance(llvm::Value* _address)
diff --git a/libevmjit/Ext.h b/libevmjit/Ext.h
index b0048d2e9..760f77df5 100644
--- a/libevmjit/Ext.h
+++ b/libevmjit/Ext.h
@@ -35,7 +35,6 @@ enum class EnvFunc
 	log,
 	blockhash,
 	extcode,
-	calldataload,  // Helper function, not client Env interface
 
 	_size
 };
diff --git a/libevmjit/Stack.cpp b/libevmjit/Stack.cpp
index 3a686c766..7cf514dea 100644
--- a/libevmjit/Stack.cpp
+++ b/libevmjit/Stack.cpp
@@ -175,32 +175,3 @@ void Stack::push(llvm::Value* _value)
 }
 }
 }
-
-extern "C"
-{
-	using namespace dev::eth::jit;
-
-	EXPORT void ext_calldataload(RuntimeData* _rtData, i256* _index, byte* o_value)
-	{
-		// It asumes all indexes are less than 2^64
-
-		auto index = _index->a;
-		if (_index->b || _index->c || _index->d)				 // if bigger that 2^64
-			index = std::numeric_limits<decltype(index)>::max(); // set max to fill with 0 leter
-
-		auto data = _rtData->callData;
-		auto size = _rtData->callDataSize;
-		for (auto i = 0; i < 32; ++i)
-		{
-			if (index < size)
-			{
-				o_value[i] = data[index];
-				++index;  // increment only if in range
-			}
-			else
-				o_value[i] = 0;
-		}
-	}
-
-} // extern "C"
-