Unknown kind of return type specified for function

I am creating a function that does not return anything so I am trying
the following:

create or replace function splite_delete_configured_selection(int, int,
int, int)
returns void
security definer
as '
declare
...
begin
...
return;
end;
' language 'plpgsql';

but as soon as I try to call this function I get the following error:

ERROR: Unknown kind of return type specified for function
splite_delete_configured_selection

How do I declare the fact that the function will return nothing?

I am running version 7.3.2.

Thanks.

Avi