HOUSTON -- Surprisingly, the Houston Astros, who lead the majors in home runs, had yet to register a walk-off homer this season, at least until second baseman Jose Altuve rendered that footnote inaccurate.

Altuve lined in ninth-inning homer into the Crawford Boxes in left field as the Houston Astros completed a three-game sweep of the Boston Red Sox with a 5-4 win Thursday night at Minute Maid Park.

Capping a 4-for-5 performance, Altuve drilled his ninth home run off Red Sox left-hander Craig Breslow (0-1), sending Boston (42-54) to its eighth consecutive loss and Houston to its ninth win in its past 10 home games.

The Astros (54-43) belted three home runs to increase their league-leading total to 135, with Altuve hitting his first career walk-off home run, one upheld following a replay review.

"I was a little scared because I didn't see it, I just saw the fans screaming," Altuve said. "They replayed it, you get scared. You don't want to go back out there, especially when you're all wet because they threw a bucket on you."

Immediately after the Astros rallied to take the lead with their three-run seventh inning, the Red Sox clawed back to pull even with two runs in the top of the eighth. The first run came immediately, with Red Sox designated hitter David Ortiz blasting a leadoff homer, his 17th, to right field off Astros right-hander Will Harris, slicing the deficit to 4-3.

Boston needed some help for the game-tying tally, capitalizing on an upheld call at second base following a Hanley Ramirez steal and a defensive miscue in left field when Preston Tucker turned a line drive from first baseman Mike Napoli into a double that scored Ramirez.

"We showed a lot of grit and a lot of fight to tie it up against their frontline guys in the bullpen," Red Sox manager John Farrell said.

The Astros did damage against the Boston bullpen, with pinch hitter Colby Rasmus smacking his 13th homer off Red Sox right-hander Alexi Ogando in the seventh and third baseman Marwin Gonzalez adding a run-scoring double off right-hander Junichi Tazawa that inning to score Altuve. Astros designated hitter Evan Gattis chipped in with an RBI single that scored shortstop Carlos Correa for a 4-2 lead.

Both Rasmus and Gattis produced exceptional at-bats, creating the momentum that carried the Astros even after the Red Sox pulled even.

"That was amazing what we did today," said Gonzalez, who finished 2-for-3 with his seventh home run and a double. "We came from behind, Colby put us in the game, and after that the game changed and we got the win. That's the most important thing. It was a tight game."

Astros right-hander Lance McCullers, making his first start since July 12, labored throughout, surrendering two doubles in the first to fall behind 1-0. Ortiz crushed a two-out, two-strike hanging curveball for an RBI double to left-center field, scoring center fielder Mookie Betts.

Boston strung together four consecutive baserunners with two outs in the second, with Napoli drilling a 3-2 curveball out to left for his 11th homer and a 2-1 lead. However, McCullers wiggled out of that jam without additional damage and worked around two two-out walks in the third inning, a leadoff double from Napoli in the fourth, and a two-out error by Correa in the fifth, keeping the Astros in position to rally once again.

"It's a tough one. We had a chance to get back in the game," said Red Sox left-hander Wade Miley, who allowed one run over six innings. "The Astros are obviously playing really good baseball right now. They're a good team over there, and they came out ahead."

NOTES: The Astros acquired LHP Scott Kazmir from the A's in exchange for two low-level prospects. Kazmir (5-5, 2.38 ERA), a Houston native, will join the club in Kansas City and start against the Royals on Friday. Houston shipped RHP Daniel Mengden and C Jacob Nottingham to Oakland in exchange for Kazmir, who is in the final season of a two-year, $22 million deal. ... The Red Sox will start RHP Rick Porcello, RHP Steven Wright and LHP Eduardo Rodriguez in that order at home against Detroit this weekend. ... Astros INF Jed Lowrie made his first rehab start Wednesday since landing on the disabled list April 27 with a right thumb ligament tear, finishing 0-for-2 while playing five innings at third base for Double-A Corpus Christi. Lowrie was given Thursday off, and he will return to the Hooks' lineup Friday, starting at third base before shifting to shortstop Saturday.