existence error

[VHILDEN]

I have been looking for a prolog implementation to run some old programs I
wrote about 15 years ago. However, I'm getting a different behavior when
trying to run a clause that doesn't exist. Basically, what I get is this:

| ?- test_proc(x).
uncaught exception: error(existence_error(procedure,test_proc/1),top_level/0)
| ?- asserta(test_proc(y)).

yes
| ?- test_proc(x).

no
| ?-

I expected it would just say "no" the first time. This "existence error" 
exception seems to be a violation of how prolog should behave.
Is it in the ISO standard?