April Novelization

The April Novelization was a set of changes to the 1952 Constitution of the [People's Republic of Poland], agreed in April 1989, in the aftermath of the Polish [Round Table Agreement].
Among key changes were:

restoration of the Senate of Poland and the post of the president of Poland
introduction of the National [Council of the Judiciary]
changes to the electoral legislation, in order to make elections more free and fair
powers of the Sejm were adjusted

The 1952 constitution would be even further reformed by the December Novelization and Small Constitution of 1992, and finally replaced in 1997 by a completely new current Constitution of Poland.