diff --git a/README.md b/README.md
index 80b859f..5a8c856 100644
--- a/README.md
+++ b/README.md
@@ -13,6 +13,9 @@ Available utilities are:
 * `p7os` will allow you to interact with the calculator's OS (backup, flash);
 * `mcsfile` will display the content of an MCS archive file.
 
+Note : for enable building/installing of `p7os` or `mcsfile` you have to use
+`--enable-<tool>` in configuration script (`--help` for more information)
+
 ## Prerequisites
 ### Making-only dependencies
 | Name                                               | Version  |