Prevent inserting document without rows

I have tables for invoice headers and rows:

CREATE TABLE invoiceheader ( id SERIAL PRIMARY KEY, .... );

CREATE TABLE invoicerow ( id SERIAL PRIMARY KEY,
idheader INTEGER NOT NULL REFERENCES invoiceheader ON DELETE CASCADE ON
UPDATE CASCADE,
....
);

Each invoice must have at leat one row.

I want that transaction commit fails if invoice header is inserted without
any row in invoice rows table.

How to prevent inserting invoice headers without rows ?

Andrus.