diff --git a/include/mbedtls/ssl_internal.h b/include/mbedtls/ssl_internal.h
index ca7beb3..579a682 100644
--- a/include/mbedtls/ssl_internal.h
+++ b/include/mbedtls/ssl_internal.h
@@ -875,11 +875,26 @@
 void mbedtls_ssl_read_version( int *major, int *minor, int transport,
                        const unsigned char ver[2] );
 
-static inline size_t mbedtls_ssl_hdr_len( const mbedtls_ssl_context *ssl )
+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 );
+}
+
+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