diff --git a/include/mbedtls/ssl_internal.h b/include/mbedtls/ssl_internal.h
index b07da39..c7668eb 100644
--- a/include/mbedtls/ssl_internal.h
+++ b/include/mbedtls/ssl_internal.h
@@ -912,28 +912,12 @@
 
 static inline size_t mbedtls_ssl_in_hdr_len( const mbedtls_ssl_context *ssl )
 {
-#if defined(MBEDTLS_SSL_PROTO_DTLS)
-    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
-    {
-        return( 13 );
-    }
-#else
-    ((void) ssl);
-#endif
-    return( 5 );
+    return( (size_t) ( ssl->in_iv - ssl->in_hdr ) );
 }
 
 static inline size_t mbedtls_ssl_out_hdr_len( const mbedtls_ssl_context *ssl )
 {
-#if defined(MBEDTLS_SSL_PROTO_DTLS)
-    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
-    {
-        return( 13 );
-    }
-#else
-    ((void) ssl);
-#endif
-    return( 5 );
+    return( (size_t) ( ssl->out_iv - ssl->out_hdr ) );
 }
 
 static inline size_t mbedtls_ssl_hs_hdr_len( const mbedtls_ssl_context *ssl )