diff --git a/core/Cargo.toml b/core/Cargo.toml
index 414917a..3943152 100644
--- a/core/Cargo.toml
+++ b/core/Cargo.toml
@@ -15,14 +15,14 @@ categories = [
 license = "MIT OR Apache-2.0"
 
 [dependencies]
-cortex-m = { version = "0.6.0", optional = true }
+critical-section = { version = "1.1", optional = true }
 
 [dependencies.defmt]
 version = "0.3.0"
 optional = true
 
 [features]
-thumbv6 = ["cortex-m"]
+thumbv6 = ["critical-section"]
 defmt_0_3 = ["defmt"]
 
 [package.metadata.docs.rs]
diff --git a/core/src/bbbuffer.rs b/core/src/bbbuffer.rs
index 78610b5..f0f9455 100644
--- a/core/src/bbbuffer.rs
+++ b/core/src/bbbuffer.rs
@@ -1108,11 +1108,11 @@ mod atomic {
         AtomicBool, AtomicUsize,
         Ordering::{self, Acquire, Release},
     };
-    use cortex_m::interrupt::free;
+    use critical_section::with;
 
     #[inline(always)]
     pub fn fetch_add(atomic: &AtomicUsize, val: usize, _order: Ordering) -> usize {
-        free(|_| {
+        with(|_| {
             let prev = atomic.load(Acquire);
             atomic.store(prev.wrapping_add(val), Release);
             prev
@@ -1121,7 +1121,7 @@ mod atomic {
 
     #[inline(always)]
     pub fn fetch_sub(atomic: &AtomicUsize, val: usize, _order: Ordering) -> usize {
-        free(|_| {
+        with(|_| {
             let prev = atomic.load(Acquire);
             atomic.store(prev.wrapping_sub(val), Release);
             prev
@@ -1130,7 +1130,7 @@ mod atomic {
 
     #[inline(always)]
     pub fn swap(atomic: &AtomicBool, val: bool, _order: Ordering) -> bool {
-        free(|_| {
+        with(|_| {
             let prev = atomic.load(Acquire);
             atomic.store(val, Release);
             prev
diff --git a/core/src/lib.rs b/core/src/lib.rs
index 49ee1bd..61c5eae 100644
--- a/core/src/lib.rs
+++ b/core/src/lib.rs
@@ -92,8 +92,11 @@
 //!
 //! This crate contains special support for Cortex-M0(+) targets with the `thumbv6` feature. By
 //! enabling the feature, unsupported atomic operations will be replaced with critical sections
-//! implemented by disabling interrupts. The critical sections are very short, a few instructions at
-//! most, so they should make no difference to most applications.
+//! using the `critical_section` crate. The critical sections are very short, a few instructions at
+//! most, so they should make no difference to most applications.  When using this feature an
+//! implementation must be provided for the `critical_section` crate.  A single core version that
+//! disables interrupts is available on the `cortex_m` crate by enabling the feature
+//! `critical-section-single-core` on that crate.
 
 #![cfg_attr(not(feature = "std"), no_std)]
 #![deny(missing_docs)]