In 1955, Nationalist Prime Minister Johannes Strijdom wanted to amend one of the entrenched clauses in the Constitution, to separate Coloured voters from whites, but his party did not have the constitutionally required two-thirds majority in a joint session of both houses of Parliament. It was decided to alter the composition and electoral system for the Senate, to enable the Separate Representation of Voters Act 1951 to be validated. Consequently, Strijdom had the Senate Act 1955 passed to amend the constitution.