diff --git a/library/ssl_tls13_keys.h b/library/ssl_tls13_keys.h
index 07b970a..a4b012f 100644
--- a/library/ssl_tls13_keys.h
+++ b/library/ssl_tls13_keys.h
@@ -657,11 +657,11 @@
  * \param[out]  out  The output buffer for the exported key. Must have room for at least out_len bytes.
  * \param[in]   out_len  Length of the key to generate.
  */
-int mbedtls_ssl_tls13_exporter(psa_algorithm_t hash_alg,
-                               const unsigned char *secret, size_t secret_len,
-                               const unsigned char *label, size_t label_len,
-                               const unsigned char *context_value, size_t context_len,
-                               unsigned char *out, size_t out_len);
+int mbedtls_ssl_tls13_exporter(const psa_algorithm_t hash_alg,
+                               const unsigned char *secret, const size_t secret_len,
+                               const unsigned char *label, const size_t label_len,
+                               const unsigned char *context_value, const size_t context_len,
+                               uint8_t *out, const size_t out_len);
 
 #endif /* MBEDTLS_SSL_PROTO_TLS1_3 */