Pie XI

If the Roman Church is to find any way out of the crisis into which nationalism has brought it, then it must be thoroughly transformed. It may be that this transformation and reformation will lead to its unconditional acceptance of the indispensability of private ownership in the means of production. At present it is still far from this, as witness the recent encyclical Quadragesimo anno.

Mises, Socialism, pp. 386f

http://w2.vatican.va/content/pius-xi/en/encyclicals/documents/hf_p-xi_enc_19310515_quadragesimo-anno.html