diff --git a/README.md b/README.md
index 433015d..c8d4363 100644
--- a/README.md
+++ b/README.md
@@ -119,6 +119,10 @@ You should use these following line of parameters:
 
 ... to enable H extension on QEMU software.
 
+3. What is the minimum supported Rust version of this package?
+
+You should build RustSBI-QEMU on nightly at least `rustc 1.66.0-nightly (a24a020e6 2022-10-18)`.
+
 ## License 
 
 This project is licensed under Mulan PSL v2.
diff --git a/rustsbi-qemu/src/main.rs b/rustsbi-qemu/src/main.rs
index b833f55..db0844b 100644
--- a/rustsbi-qemu/src/main.rs
+++ b/rustsbi-qemu/src/main.rs
@@ -1,6 +1,6 @@
 #![no_std]
 #![no_main]
-#![feature(naked_functions, asm_sym, asm_const)]
+#![feature(naked_functions, asm_const)]
 #![deny(warnings)]
 
 mod clint;
diff --git a/test-kernel/src/main.rs b/test-kernel/src/main.rs
index 4a2fa79..b3327d0 100644
--- a/test-kernel/src/main.rs
+++ b/test-kernel/src/main.rs
@@ -1,6 +1,6 @@
 #![no_std]
 #![no_main]
-#![feature(naked_functions, asm_sym, asm_const)]
+#![feature(naked_functions, asm_const)]
 #![deny(warnings)]
 
 #[macro_use]