how to use $^ automatic variable with prerequisites built on target-specific variable ?

[Axel]

Hello

I m using a target with prerequisites based on target-specific variable, 
but it seems that the $^ doesn't work and is empty in this use-case :

prereq:
    touch prereq

test: FILE = prereq

test: $(FILE)
    echo Variable: $(FILE) Prereq: $^


"make test" displays that $^ is empty, but the prerequesites are checked 
and built. Is this a normal behaviour ? The workaround for me is to use 
$(FILE) rather than $^ but I assumed that $^ would have worked.

Thanks in advance.