BERLIN — Insulting a king used to be dangerous business, but in the Netherlands, it could soon be the legal equivalent of trash-talking an ambulance driver.

Under Dutch law, insulting the monarch is a crime — though it is rarely prosecuted — punishable by up to five years in prison. But the lower house of Parliament voted on Tuesday to reduce the maximum sentence to four months for speaking ill of the king, his immediate family, or any other head of state, putting them on the same level as police officers, emergency room workers, social workers and ambulance drivers.

“Our king, Willem-Alexander, and of course other heads of state should not be insulted, but if it does happen, then everyone should be equal in front of the law,” said Kees Verhoeven, a lawmaker with the leftist party Democrats 66, who introduced the bill.

The 120-to-30 vote sent the bill to the upper house of Parliament, where it is expected to get approval.