diff --git a/sys/kern/kern_umtx.c b/sys/kern/kern_umtx.c
index 1e93a66805b1..31a5cb1964e7 100644
--- a/sys/kern/kern_umtx.c
+++ b/sys/kern/kern_umtx.c
@@ -756,6 +756,5 @@ _umtx_op(struct thread *td, struct _umtx_op_args *uap)
 		error = EINVAL;
 		break;
 	}
-	td->td_retval[0] = -error;
-	return (0);
+	return (error);
 }
diff --git a/sys/sys/umtx.h b/sys/sys/umtx.h
index c9cfcb702359..527beb9234e3 100644
--- a/sys/sys/umtx.h
+++ b/sys/sys/umtx.h
@@ -81,7 +81,8 @@ umtx_lock(struct umtx *umtx, long id)
 {
 	if (atomic_cmpset_acq_ptr(&umtx->u_owner, (void *)UMTX_UNOWNED,
 	    (void *)id) == 0)
-		return (- _umtx_op(umtx, UMTX_OP_LOCK, id, 0, 0));
+		if (_umtx_op(umtx, UMTX_OP_LOCK, id, 0, 0) == -1)
+			return (errno);
 	return (0);
 }
 
@@ -99,7 +100,8 @@ umtx_timedlock(struct umtx *umtx, long id, const struct timespec *timeout)
 {
 	if (atomic_cmpset_acq_ptr(&umtx->u_owner, (void *)UMTX_UNOWNED,
 	    (void *)id) == 0)
-		return (- _umtx_op(umtx, UMTX_OP_LOCK, id, 0, (void *)timeout));
+		if (_umtx_op(umtx, UMTX_OP_LOCK, id, 0, (void *)timeout) == -1)
+			return (errno);
 	return (0);
 }
 
@@ -108,21 +110,26 @@ umtx_unlock(struct umtx *umtx, long id)
 {
 	if (atomic_cmpset_rel_ptr(&umtx->u_owner, (void *)id,
 	    (void *)UMTX_UNOWNED) == 0)
-		return (- _umtx_op(umtx, UMTX_OP_UNLOCK, id, 0, 0));
+		if (_umtx_op(umtx, UMTX_OP_UNLOCK, id, 0, 0) == -1)
+			return (errno);
 	return (0);
 }
 
 static __inline int
 umtx_wait(struct umtx *umtx, long id, const struct timespec *timeout)
 {
-	return (- _umtx_op(umtx, UMTX_OP_WAIT, id, 0, (void *)timeout));
+	if (_umtx_op(umtx, UMTX_OP_WAIT, id, 0, (void *)timeout) == -1)
+		return (errno);
+	return (0);
 }
 
 /* Wake threads waiting on a user address. */
 static __inline int
 umtx_wake(struct umtx *umtx, int nr_wakeup)
 {
-	return (- _umtx_op(umtx, UMTX_OP_WAKE, nr_wakeup, 0, 0));
+	if (_umtx_op(umtx, UMTX_OP_WAKE, nr_wakeup, 0, 0) == -1)
+		return (errno);
+	return (0);
 }
 
 #endif /* !_KERNEL */