diff --git a/include/mbedtls/ssl_internal.h b/include/mbedtls/ssl_internal.h
index 35a461e..1a70677 100644
--- a/include/mbedtls/ssl_internal.h
+++ b/include/mbedtls/ssl_internal.h
@@ -1095,6 +1095,8 @@
 
 int mbedtls_ssl_start_renegotiation( mbedtls_ssl_context *ssl );
 
+size_t mbedtls_ssl_get_current_mtu( const mbedtls_ssl_context *ssl );
+
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
 void mbedtls_ssl_buffering_free( mbedtls_ssl_context *ssl );
 void mbedtls_ssl_flight_free( mbedtls_ssl_flight_item *flight );