Yainer Diaz added a three-run homer as AL West-leading Houston extended its winning streak to five games.

The Astros scored four runs in the third off Cubs starter Cade Horton (3-2), with Jose Altuve scoring on a sacrifice fly by Victor Caratini before Diaz capped the inning with his 377-foot shot to left-center.

Smith, a first-round draft selection by Chicago last year was acquired by the Astros in the offseason as part of the deal for Kyle Tucker, extended Houston´s lead to 7-0 in the fourth with his home run off the left field façade, his sixth of the season. Smith had two hits and scored two runs.

Walter (1-1), a 28-year-old left-hander, allowed one run on four hits with five strikeouts. Josh Hader got the final out for his 22nd save.

Jeremy Peña exited in the fifth with left rib soreness. He was hit by a pitch in his left side in the second. There was no immediate word on the extent of his injury.

Nico Hoerner hit a solo home run in the fifth, and Matt Shaw added a two-run double in the seventh and an RBI double in the ninth for NL Central-leading Chicago.

Horton allowed seven runs on eight hits with four walks in four innings.

Tucker was hitless in his return to Houston. He kept the game scoreless in the first, throwing Isaac Paredes out at the plate to end the frame.

Hader inducing a lineout to center by Ian Happ to end it with Tucker, representing the tying run, on deck.

Houston has its second five-game winning streak for the month of June, and improved to an MLB-best 18-6 this month.

Cubs RHP Colin Rea (4-3, 4.42 ERA) starts the second game of the three-game series Saturday. Lance McCullers Jr. (1-2, 4.91) is expected to come off the 15-day injured list and start for Houston.