FormBuilder and FEU $username variable

[Orthim]

Hello

I've been tinkering around with formbuilder and frontendusers, to make a form update into a database by using a custom tag. The only problem now is that the $username variable won't be transferred.
When i use a hidden field and the smarty tag {$username} - i have called the module beforehand of course and that works fine - while letting formbuilder parse it as a smarty tag, the error

Code: Select all

string(130) "Smarty error: [in evaluated template line 1]: syntax error: unrecognized tag: $username (Smarty_Compiler.class.php, line 446)"
string(117) "Smarty error: [in evaluated template line 1]: syntax error: unrecognized tag '' (Smarty_Compiler.class.php, line 590)"

occurs, thus putting a die on the form and still not passing the $username variable. When I input my own into the form, it does not pass on at all and, same as before, no use with the $username thing.

What should I do to get it working?