Sapronov was expelled from the party at the fifteenth Party Congress in December 1927 and sentenced to three years exile in Arkhangelsk. When the decision was reported to them, he and Smirnov signed a protest claiming that they did not know what they were accused of, and that "the OGPU does not and cannot have any facts about our anti-Soviet work. Our work of late has been to defend within the party our views set out in the Platform of the 15..."
