diff --git a/runtime/doc/starting.txt b/runtime/doc/starting.txt
index f56baf6..bca2f97 100644
--- a/runtime/doc/starting.txt
+++ b/runtime/doc/starting.txt
@@ -256,6 +256,8 @@
 		Interfaces, such as Python, Ruby and Lua, are also disabled,
 		since they could be used to execute shell commands.  Perl uses
 		the Safe module.
+		For Unix restricted mode is used when the last part of $SHELL
+		is "nologin" or "false".
 		Note that the user may still find a loophole to execute a
 		shell command, it has only been made difficult.