diff --git a/arch/arm/core/swap.c b/arch/arm/core/swap.c
index 204fe263cf5..f0de57d22f8 100644
--- a/arch/arm/core/swap.c
+++ b/arch/arm/core/swap.c
@@ -41,11 +41,11 @@ extern const int _k_neg_eagain;
  * On ARMv6-M, the intlock key is represented by the PRIMASK register,
  * as BASEPRI is not available.
  *
- * @return may contain a return value setup by a call to
+ * @return -EAGAIN, or a return value set by a call to
  * _set_thread_return_value()
  *
  */
-unsigned int __swap(int key)
+int __swap(int key)
 {
 #ifdef CONFIG_USERSPACE
 	/* Save off current privilege mode */
diff --git a/arch/posix/core/swap.c b/arch/posix/core/swap.c
index 6278764be9f..3240e7bbba5 100644
--- a/arch/posix/core/swap.c
+++ b/arch/posix/core/swap.c
@@ -34,7 +34,7 @@
  *
  */
 
-unsigned int __swap(unsigned int key)
+int __swap(unsigned int key)
 {
 /*
  * struct k_thread * _kernel.current is the currently runnig thread
diff --git a/kernel/include/kswap.h b/kernel/include/kswap.h
index a838498df87..01ac1f07533 100644
--- a/kernel/include/kswap.h
+++ b/kernel/include/kswap.h
@@ -40,7 +40,7 @@ void _smp_release_global_lock(struct k_thread *thread);
  * Needed for SMP, where the scheduler requires spinlocking that we
  * don't want to have to do in per-architecture assembly.
  */
-static inline unsigned int _Swap(unsigned int key)
+static inline int _Swap(unsigned int key)
 {
 	struct k_thread *new_thread, *old_thread;
 	int ret = 0;
@@ -90,11 +90,11 @@ static inline unsigned int _Swap(unsigned int key)
 
 #else /* !CONFIG_USE_SWITCH */
 
-extern unsigned int __swap(unsigned int key);
+extern int __swap(unsigned int key);
 
-static inline unsigned int _Swap(unsigned int key)
+static inline int _Swap(unsigned int key)
 {
-	unsigned int ret;
+	int ret;
 	_check_stack_sentinel();
 	_update_time_slice_before_swap();