The Astros recalled Ullola from Triple-A Sugar Land prior to Sunday's game against the White Sox.
Houston demoted Kai-Wei Teng to clear a spot on the 26-man active roster and in the bullpen for Ullola, who will join the big club for the second time this season after striking out seven over four scoreless innings in two appearances during his first stint in the majors. Ullola had earned his way back to Houston after striking out nine over 5.1 perfect innings in his last six relief outings at Sugar Land.