Apple

I've got a problem using code under leopard and tiger.

I don't know exactly what's the problem, so let me ask you.

The following code works with leopard ( 10.5.x )

    tell application "Finder"
        set selectionList to the selection as alias list
        repeat with itemAlias in selectionList
            if (class of item itemAlias) is folder then
                set itemisfolder to "1"
            else
                set itemisfile to "1"
            end if
        end repeat

but with tiger ( 10.4.11 ) I've got the following error:

AppleScript Error:
alias "Tiger:Users:tobias:Desktop:3050_0011.pdf" cannot be converted to type <<class alst>>

I hope there's someone with an idea whats wrong with those lines.

thanks in advance..

Tobias