PLPGSQL/EXCEPTION HANDLING

["renneyt@xxxxxxxxx" <renneyt@xxxxxxxxx>]

In a function implemented in 7.4.8 I had the following error when I call 
the function:

ERROR:  syntax error at or near "EXCEPTION"

Offending line is:
   EXCEPTION WHEN dup_val_on_index THEN NULL;

When this line is removed, all is well.

Any help appreciated...