diff --git a/ff/src/biginteger/macros.rs b/ff/src/biginteger/macros.rs
index 138b05af6..ce2bed4de 100644
--- a/ff/src/biginteger/macros.rs
+++ b/ff/src/biginteger/macros.rs
@@ -17,7 +17,16 @@ macro_rules! bigint_impl {
                 let mut carry = 0;
 
                 for i in 0..$num_limbs {
-                    self.0[i] = adc!(self.0[i], other.0[i], &mut carry);
+                    #[cfg(all(target_arch = "x86_64", feature = "asm"))]
+                    #[cfg_attr(all(target_arch = "x86_64", feature = "asm"), allow(unsafe_code))]
+                    unsafe { 
+                        carry = core::arch::x86_64::_addcarry_u64(carry, self.0[i], other.0[i], &mut self.0[i]) 
+                    };
+
+                    #[cfg(not(feature = "asm"))]
+                    {
+                        self.0[i] = adc!(self.0[i], other.0[i], &mut carry);
+                    }
                 }
 
                 carry != 0
@@ -28,7 +37,16 @@ macro_rules! bigint_impl {
                 let mut borrow = 0;
 
                 for i in 0..$num_limbs {
-                    self.0[i] = sbb!(self.0[i], other.0[i], &mut borrow);
+                    #[cfg(all(target_arch = "x86_64", feature = "asm"))]
+                    #[cfg_attr(all(target_arch = "x86_64", feature = "asm"), allow(unsafe_code))]
+                    unsafe { 
+                        borrow = core::arch::x86_64::_subborrow_u64(borrow, self.0[i], other.0[i], &mut self.0[i]) 
+                    };
+
+                    #[cfg(not(feature = "asm"))]
+                    {
+                        self.0[i] = sbb!(self.0[i], other.0[i], &mut borrow);
+                    }
                 }
 
                 borrow != 0
diff --git a/ff/src/lib.rs b/ff/src/lib.rs
index db280fa90..72ec5669d 100644
--- a/ff/src/lib.rs
+++ b/ff/src/lib.rs
@@ -1,9 +1,9 @@
 #![cfg_attr(not(feature = "std"), no_std)]
 #![warn(unused, future_incompatible, nonstandard_style, rust_2018_idioms)]
 #![allow(clippy::op_ref, clippy::suspicious_op_assign_impl)]
-#![cfg_attr(not(use_asm), forbid(unsafe_code))]
+#![cfg_attr(not(feature = "asm"), forbid(unsafe_code))]
 #![cfg_attr(use_asm, feature(llvm_asm))]
-#![cfg_attr(use_asm, deny(unsafe_code))]
+#![cfg_attr(feature = "asm", deny(unsafe_code))]
 
 #[macro_use]
 extern crate ark_std;