diff --git a/library/ssl_msg.c b/library/ssl_msg.c
index dbc6391..085233c 100644
--- a/library/ssl_msg.c
+++ b/library/ssl_msg.c
@@ -511,15 +511,12 @@
                                     unsigned char const *dynamic_iv,
                                     size_t dynamic_iv_len )
 {
-    size_t i;
-
     /* Start with Fixed IV || 0 */
     memset( dst_iv, 0, dst_iv_len );
     memcpy( dst_iv, fixed_iv, fixed_iv_len );
 
     dst_iv += dst_iv_len - dynamic_iv_len;
-    for( i = 0; i < dynamic_iv_len; i++ )
-        dst_iv[i] ^= dynamic_iv[i];
+    mbedtls_xor( dst_iv, dst_iv, dynamic_iv, dynamic_iv_len );
 }
 #endif /* MBEDTLS_GCM_C || MBEDTLS_CCM_C || MBEDTLS_CHACHAPOLY_C */