diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index 496ebe968..e76c9be0e 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -1262,11 +1262,8 @@
  *
  * Enable key identifiers that encode a key owner identifier.
  *
- * This is only meaningful when building the library as part of a
- * multi-client service. When you activate this option, you must provide an
- * implementation of the type mbedtls_key_owner_id_t and a translation from
- * mbedtls_svc_key_id_t to file name in all the storage backends that you
- * you wish to support.
+ * The owner of a key is identified by a value of type ::mbedtls_key_owner_id_t
+ * which is currently hard-coded to be int32_t.
  *
  * Note that this option is meant for internal use only and may be removed
  * without notice.
diff --git a/include/psa/crypto_platform.h b/include/psa/crypto_platform.h
index 4e2f162ea..c64f61d58 100644
--- a/include/psa/crypto_platform.h
+++ b/include/psa/crypto_platform.h
@@ -54,8 +54,15 @@ typedef uint16_t psa_key_handle_t;
 
 #if defined(MBEDTLS_PSA_CRYPTO_KEY_ID_ENCODES_OWNER)
 
-/* Building for the PSA Crypto service on a PSA platform. */
-/* A key owner is a PSA partition identifier. */
+/* Building for the PSA Crypto service on a PSA platform, a key owner is a PSA
+ * partition identifier.
+ *
+ * The function psa_its_identifier_of_slot() in psa_crypto_storage.c that
+ * translates a key identifier to a key storage file name assumes that
+ * mbedtls_key_owner_id_t is an 32 bits integer. This function thus needs
+ * reworking if mbedtls_key_owner_id_t is not defined as a 32 bits integer
+ * here anymore.
+ */
 typedef int32_t mbedtls_key_owner_id_t;
 
 /** Compare two key owner identifiers.