‘Abdu’l-Baha had already considered establishing the Universal House of Justice when Shoghi Effendi was still a child

‘Abdu’l-Baha had already considered establishing the Universal House of Justice when Shoghi Effendi was still a child in case he, ‘Abdu’l-Baha, should be separated from the community through death or imprisonment in solitary confinement. As a precaution, he therefore gave instructions for the election of the Universal House of Justice to Haji Mirza Taqi Afnan, the architect of the House of Worship in ‘Ishqabad (letter from the Universal House of Justice dated 9 March 1965, in Wellspring of Guidance, pp. 48f.).

(Making the Crooked Straight: A Contribution to Bahá'í Apologetics, by Udo Schaefer, p. 721)