diff --git a/rust-toolchain b/rust-toolchain
index 2e62589..76d0536 100644
--- a/rust-toolchain
+++ b/rust-toolchain
@@ -1 +1 @@
-nightly-2021-11-17
+1.62.0
diff --git a/src/bn256/assembly.rs b/src/bn256/assembly.rs
index 6d56639..ad28f67 100644
--- a/src/bn256/assembly.rs
+++ b/src/bn256/assembly.rs
@@ -4,6 +4,8 @@ macro_rules! assembly_field {
             /// Doubles this field element.
             #[inline]
             pub fn double(&self) -> $field {
+                use core::arch::asm;
+
                 let mut r0: u64;
                 let mut r1: u64;
                 let mut r2: u64;
@@ -59,6 +61,8 @@ macro_rules! assembly_field {
             /// Squares this element.
             #[inline]
             pub fn square(&self) -> $field {
+                use core::arch::asm;
+
                 let mut r0: u64;
                 let mut r1: u64;
                 let mut r2: u64;
@@ -347,6 +351,8 @@ macro_rules! assembly_field {
 
             #[inline(always)]
             pub(crate) fn montgomery_reduce(a: &[u64; 8]) -> $field {
+                use core::arch::asm;
+
                 let mut r0: u64;
                 let mut r1: u64;
                 let mut r2: u64;
@@ -533,6 +539,8 @@ macro_rules! assembly_field {
             /// Multiplies `rhs` by `self`, returning the result.
             #[inline]
             pub fn mul(&self, rhs: &Self) -> $field {
+                use core::arch::asm;
+
                 let mut r0: u64;
                 let mut r1: u64;
                 let mut r2: u64;
@@ -823,6 +831,8 @@ macro_rules! assembly_field {
             /// Subtracts `rhs` from `self`, returning the result.
             #[inline]
             pub fn sub(&self, rhs: &Self) -> $field {
+                use core::arch::asm;
+
                 let mut r0: u64;
                 let mut r1: u64;
                 let mut r2: u64;
@@ -879,6 +889,8 @@ macro_rules! assembly_field {
             /// Adds `rhs` to `self`, returning the result.
             #[inline]
             pub fn add(&self, rhs: &Self) -> $field {
+                use core::arch::asm;
+
                 let mut r0: u64;
                 let mut r1: u64;
                 let mut r2: u64;
@@ -935,6 +947,8 @@ macro_rules! assembly_field {
             /// Negates `self`.
             #[inline]
             pub fn neg(&self) -> $field {
+                use core::arch::asm;
+
                 let mut r0: u64;
                 let mut r1: u64;
                 let mut r2: u64;
diff --git a/src/lib.rs b/src/lib.rs
index 61756bb..e9176b4 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,5 +1,4 @@
-#![feature(asm)]
-#![feature(asm_const)]
+#![cfg_attr(feature = "asm", feature(asm_const))]
 
 #[macro_use]
 mod ec;