HELP- cant find "gtk_object_check_cast"

[Robert_A_Grabau fmso navy mil]

GTKer's:

While trying to compile the latest xwhois, I run into a compile problem with 
undefined reference:
gtk_object_check_cast
Which header file is this in? Grepping my way through the include files does 
not find it.
Now for some info on my config - 
gtk 1.0.6 (rpm) & development 1.06 rpm
gnome's 0.30 rpm's installed (all - current) - which means I have some of the 
1.1.x stuff installed
(which maybe my problem).
Any help would be appreciated.

TIA
bob