Trigger for a simple check doesnt allow Macros

Steps to reproduce the issue:

Add Template 'TEST' with Macro {$TESTPORT} and assign it value of 80
Add Item with Key 'tcp,{$TESTPORT}' and Save
This works
But now when I add a trigger for this Item, like '{Test:tcp,{$TESTPORT}.last(0)}=0' and press Save the following error comes up:

Incorrect item key "tcp,{$TESTPORT" is used in expression. Incorrect simple check parameter.
Check expression part starting from " {Test:tcp,{$TESTPORT}.last(0)}=0 "