diff --git a/README.md b/README.md
index 420ea87a1..975b8f141 100644
--- a/README.md
+++ b/README.md
@@ -16,6 +16,8 @@ git clone https://github.com/riscv-software-src/riscv-isa-sim
 cd riscv-isa-sim
 cp -r arch_test_target/spike/device/rv32i_m/I arch_test_target/spike/device/rv32i_m/F
 <edit arch_test_target/spike/device/rv32i_m/F/Makefile.include line 35 and change --isa=rv32i to --isa=rv32if>
+cp -r arch_test_target/spike/device/rv32i_m/I arch_test_target/spike/device/rv64i_m/D
+<edit arch_test_target/spike/device/rv64i_m/D/Makefile.include line 35 and change --isa=rv64i to --isa=rv64id>
 mkdir build
 cd build
 set RISCV=/cad/riscv/gcc/bin   (or whatever your path is)