diff --git a/library/ecp.c b/library/ecp.c
index ca49f99..cc8a26c 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -1160,8 +1160,8 @@
     /*
      * Next two bytes are the namedcurve value
      */
-    buf[0] = curve_info->tls_id >> 8;
-    buf[1] = curve_info->tls_id & 0xFF;
+    buf[0] = MBEDTLS_BYTE_1( curve_info->tls_id );
+    buf[1] = MBEDTLS_BYTE_0( curve_info->tls_id );
 
     return( 0 );
 }