A "seven nation army" couldn't hold Jack White back. In fact, it may have encouraged him to join Pearl Jam for their encore at Portugal's NOS Alive festival Saturday night (July 14). White, who had played just prior to Pearl Jam, joined Eddie Vedder and the band for closing performance of a cover of Neil Young's "Rockin' in the Free World," as seen in the fan-shot video above.

Pearl Jam offered White a little bit of encouragement earlier during their encore, tagging the familiar "Seven Nation Army" riff to get fans chanting along in between their cover of Pink Floyd's "Comfortably Numb" and their early era favorite "Porch." Additional fan shot video can be seen below.

In all, Pearl Jam played a 24-song set to close out the night, including a five-song encore that also opened with a performance of John Lennon's "Imagine." White, who as stated played earlier in the evening for the fans in Portugal, had delivered at 15-song set that closed out with a rousing rendition of "Seven Nation Army."

Pearl Jam's European tour wraps Tuesday (July 17) in London, with the band returning stateside on Aug. 8 in Seattle to start a U.S. tour of baseball stadiums. See their stops here. White is also wrapping up a European run, playing in Finland tonight (July 15). He'll resume his touring Aug. 5 at Chicago's Lollapalooza. See White's tour dates here.

Pearl Jam Albums Ranked

10 Best Pearl Jam Songs