Error building taskmanager 0.40

[Tom Weeds]

Tried to build the latest and greatest taskmanager on Debian Etch and
got the following error message.

xfce4_taskmanager-interface.o: In function `create_main_window':
/home/mepis32/tmp/xfce4-taskmanager-0.4.0/src/interface.c:82:
undefined reference
to `gtk_tree_view_set_show_expanders

Is my version of the GTK out of date?
Will I have to wait for the next Debian release due out in September?

Thanks for any advice offered ....