diff --git a/sys/kern/kern_umtx.c b/sys/kern/kern_umtx.c
index 8ff8f764dedb..cf472912164b 100644
--- a/sys/kern/kern_umtx.c
+++ b/sys/kern/kern_umtx.c
@@ -793,7 +793,7 @@ umtxq_sleep(struct umtx_q *uq, const char *wmesg, struct abs_timeout *abstime)
  * Convert userspace address into unique logical address.
  */
 int
-umtx_key_get(void *addr, int type, int share, struct umtx_key *key)
+umtx_key_get(const void *addr, int type, int share, struct umtx_key *key)
 {
 	struct thread *td = curthread;
 	vm_map_t map;
diff --git a/sys/sys/umtx.h b/sys/sys/umtx.h
index 07794dfe038b..145950710a10 100644
--- a/sys/sys/umtx.h
+++ b/sys/sys/umtx.h
@@ -153,7 +153,7 @@ umtx_key_match(const struct umtx_key *k1, const struct umtx_key *k2)
 }
 
 int umtx_copyin_timeout(const void *, struct timespec *);
-int umtx_key_get(void *, int, int, struct umtx_key *);
+int umtx_key_get(const void *, int, int, struct umtx_key *);
 void umtx_key_release(struct umtx_key *);
 struct umtx_q *umtxq_alloc(void);
 void umtxq_free(struct umtx_q *);