Cannot use variable for Icon (path to local .ico) in Control Panel or Shortcut window

Following happens with a very simple installation:

Create a project with a single .exe file.

Create a variable called MyAppIcon that has value: ..\..\Commun\TCG-AIR\AIRC.ico
Variable name and value do not seem to matter anyway.

Create a shortcut and use $(var.MyAppIcon) as custom icon
and/or:
Use $(var.MyAppIcon) as Icon for the Control Panel

In this context, I run the build and get in the log window:
...
setup.wxs
...\setup.wxs(55) : error CNDL0014 : The Shortcut/@Icon attribute's value, 'i_0001.MyAppIcon)', is not a legal identifier. Identifiers may contain ASCII characters A-Z, a-z, digits, underscores (_), or periods (.). Every identifier must begin with either a letter or an underscore.
...\setup.wxs(59) : error CNDL0014 : The Icon/@Id attribute's value, 'i_0001.MyAppIcon)', is not a legal identifier. Identifiers may contain ASCII characters A-Z, a-z, digits, underscores (_), or periods (.). Every identifier must begin with either a letter or an underscore.
Error 4001: candle.exe returned 14

Seems that the variable name is badly manipulated : 'i_0001.MyAppIcon)' instead of 'MyAppIcon'

Everything seems Ok (to me) in project file.
I join project file and log file for analysis (took me some time to understand I need to ZIP the attachment to allow upload).

Just found a partial workaround:
use a variable called MyAppIconDir that has value: ..\..\Commun\TCG-AIR
and specify the file name where needed: $(var.MyAppIconDir)\AIRC.ico

Philippe