though he remained a close associate of Pilsudski, he did not come to Warsaw for the 1926 May Coup, remaining in Wilno, together with Edward Śmigły-Rydz. After the coup, Prystor was moved by Pilsudski to the office of the Minister of Military Affairs, and for the next three years, he followed Pilsudski, attending all meetings and military councils, including those marked as top secret. On April 30, 1927, he was promoted to lieutenant colonel (Podpolkovnik), and began working at the Main Office of the General Inspector of the Armed Forces, where he was responsible for the removal of those officers who opposed the Sanacja regime. Prystor was one of the few men in Poland with direct access to Pilsudski, at any time of the day and night. He lived in the Belweder, together with the Marshal. In 1929, he was briefly manager of the Personal Officer of the Ministry of Military Affairs. On April 26, 1929, he was named the Minister of Labour and Social Services in the government of Kazimierz Bartel. Working under very difficult conditions, as Poland was affected by the Great Depression, Prystor managed to increase unemployment benefits and increase the program of Public works. Furthermore, he dissolved the structures of the government health insurance program, which were in the hands of oppositional Polish Socialist Party. Among others, Prystor introduced government commissars into local offices of health insurance. After the collapse of the government of Kazimierz Świtalski, Prystor once again became the Minister of Labour and Social Services, in the fifth government of Kazimierz Bartel. He remained in this post in the governments of Walery Sławek and Józef Piłsudski. In 1931, he was elected to the Sejm, as a member of the pro-government Nonpartisan Bloc for Cooperation with the Government (BBWR), remaining in the Polish Parliament until 1935. In December 1930, Prystor was appointed the Minister of Trade and Industry, and on May 27, 1931, he became the Prime Minister of Poland. He was regarded as a poor premier, avoiding any reforms. His policies resulted in decrease of investment and deepened recession. Prystor remained in his post until May 1933, when Józef Piłsudski demanded his dismissal. The reason for this most likely was a personal conflict between Prystor's wife Janina, and Pilsudski's wife Aleksandra Pilsudska. In 1934, Prystor went on a private trip to Lithuania, during which he talked with main Lithuanian politicians, including President Antanas Smetona.