Objectloop different in 6.33?

[TotlNoob]

Hi, all. Trying to get back into Inform6. Objectloop isn't behaving. The statement:
Objectloop(x ofclass Gbutton)...

tells me "expected variable but found x". Has it changed, or am I missing something?

[TotlNoob]

Found it! Didn't initialize the objectloop variable.
Making all the rookie mistakes again...