diff --git a/library/ssl_tls13_server.c b/library/ssl_tls13_server.c
index 2ee67bf..7114501 100644
--- a/library/ssl_tls13_server.c
+++ b/library/ssl_tls13_server.c
@@ -1403,7 +1403,7 @@
     ret = mbedtls_ssl_write_alpn_ext( ssl, p, end, &output_len );
     if( ret != 0 )
         return( ret );
-    p  += output_len;
+    p += output_len;
 #endif /* MBEDTLS_SSL_ALPN */
 
     extensions_len = ( p - p_extensions_len ) - 2;