https://github.com/wiz-lang/wiz/blob/5a8ea1ce15953d6ed9d222a54a31cb6447c79121/src/wiz/platform/z80_platform.cpp#L887C156-L887C158 Currently: builtins.createInstruction(InstructionSignature(InstructionType::LoadIntrinsic(io_read), 0, {std::get<0>(reg), patternC}), encodingImplicit, InstructionOptions({prefixExtended, static_cast<std::uint8_t>((std::get<1>(reg) * 8))}, {}, {})); Update to: builtins.createInstruction(InstructionSignature(InstructionType::LoadIntrinsic(io_read), 0, {std::get<0>(reg), patternC}), encodingImplicit, InstructionOptions({prefixExtended, static_cast<std::uint8_t>((std::get<1>(reg) * 8)|0x40)}, {}, {}));