#48 Expression "is null" not recognized

[Jack Walla]

PL/SQL containing a line like the following results in
a parse error:

if x is null then
x=1;
end if;

Last consumed token: "x"
net.sourceforge.pldoc.parser.ParseException:
Encountered "is" at line 6, column 13.
Was expecting one of:
"THEN" ...
"(" ...