Issue with function @key parameters

I have noticed an issue with @key parameter default values not getting processed correctly...

Below is an example code segment:

procedure( test_code(
@key ( PseudoName "psuedo_tp")
( PreFix "_TP")
( Debug t)
)
let((Mark PreFix Comps net count Status)
when(Debug printf("PseudoName %A PreFix %A Debug %A\n" PseudoName PreFix Debug))
;; initialize variables
(count = 0)
unless(stringp(PseudoName) (PseudoName = "PSUEDO_TP"))
unless(stringp(PreFix) (PreFix = "_TP"))
when(Debug printf("PseudoName %A PreFix %A Debug %A\n" PseudoName PreFix Debug))
)
)

When I run this is Allegro, the Prefix parameter default value of "_TP" is discarded, as shown below:

\i (00:00:47) skill test_code
(00:00:47) PseudoName "psuedo_tp" PreFix nil Debug t
(00:00:47) PseudoName "psuedo_tp" PreFix "_TP" Debug t
(00:00:47) t

Has anyone else seen this issue? if so, what is the solution...