diff --git a/deploy_checkit_tiff/README.txt b/deploy_checkit_tiff/README.txt
index d6b40a2a52d80e62c7411c07195326d7b5b549cd..ab73b4f822b6d62039a93d4e020c16a094879b3e 100644
--- a/deploy_checkit_tiff/README.txt
+++ b/deploy_checkit_tiff/README.txt
@@ -8,6 +8,9 @@ How to build checkit-tiff variants for Redhat system used by Rosetta
 == Prerequisites
 
 * you need 'docker'
+* If using Debian buster or higher, you must(!) add "vsyscall=emulate" option
+to the Linux kernel boot option, because CentOS 6.xx triggers syscalls in an
+outdated way.
 
 == How to build