diff --git a/source/reference-manual/security/secure-machines.rst b/source/reference-manual/security/secure-machines.rst
index 5cf32ddd5..721b230d7 100644
--- a/source/reference-manual/security/secure-machines.rst
+++ b/source/reference-manual/security/secure-machines.rst
@@ -60,7 +60,6 @@ configuration::
         DISTRO: lmp-mfgtool
         IMAGE: mfgtool-files
         EXTRA_ARTIFACTS: mfgtool-files.tar.gz
-        UBOOT_SIGN_ENABLE: "1"
 
 How to use
 ----------