SAN FRANCISCO (AP) - Johnathan Williams scored 17 points and Josh Perkins added 16 to lead No. 15 Gonzaga to its 18th straight road victory in the West Coast Conference, 75-65 over San Francisco on Saturday night.

The Bulldogs (16-3, 6-0) got a rare test in conference play after winning their first five games by at least 29 points. But they were up to the task with help from two key blocked shots late by Rei Hachimura.

Silas Melson had 14 points and Hachimura added 10 as Gonzaga was held nearly 16 points below the its season average but still managed to win its 12th straight in the series.

Souley Boum scored 22 points and Frankie Ferrari added 18 for the Dons (10-9, 2-4). San Francisco has lost 14 straight games against ranked opponents since beating Gonzaga at home 66-65 on Feb. 12, 2012.

The Dons managed to cut what had been a 12-point deficit in the first half down to five on a 3-pointer by Ferrari early in the second half. But USF them missed seven of its next eight shots from the field as Gonzaga back up to 14 on a 3-pointer by Perkins just past the midpoint of the half.

Jan 13, 2018; San Francisco, CA, USA; Gonzaga Bulldogs forward Johnathan Williams (3) dribbles against the San Francisco Dons in the first half at War Memorial Gymnasium. Mandatory Credit: John Hefti-USA TODAY Sports