Paul Schrader had a special job on the set of his latest film, “Oh, Canada”: drawing on the jockstrap that Jacob Elordi wears in one of the Vietnam War drama’s pivotal scenes.

There’s a choice at the heart of “Oh, Canada,” when the fictional filmmaker Leonard Fife (played as a young man by Elordi, and older man as Richard Gere) dodges the Vietnam draft and escapes to Canada. The script leaves breadcrumbs as to what exactly happens until very late in the film, but finally Elordi is seen reporting for an Army physical. He shows up in a jockstrap with “peace and love” written on the jock, surrounded by tiny flowers. He jitters and shakes and waves his arms flamboyantly. In character, Elordi is attempting to look as unstable (and, frankly, homosexual) as possible to avoid enlisting into military service.

At the Cannes Film Festival press conference for the film, Schrader revealed that he added a finishing touch to the jockstrap that Elordi’s character wears during the scene.

“I embellished [his jockstrap] myself with a magic marker,” Schrader said in a response to a question from Variety. “I think the wardrobe people were a little afraid to do too much so I took that burden off their shoulders.”

Schrader reflected on a “two to three year period where all young American men had to make a decision” regarding the draft. Schrader said he was deferred from service for medical reasons. Friends of his were drafted, and others wandered around the country evading Uncle Sam. He even shouted out “Oliver Stone, who went to Vietnam and won an Oscar.” Indeed, Stone served in the ’60s and was twice wounded in action.

Schrader’s latest film premiered on Friday night to a four-minute standing ovation, although Elordi was absent because he is filming Guillermo del Toro’s “Frankenstein.” After the ovation finished, Schrader addressed Elordi not being there, saying: “I’m very happy with Richard, Uma, Jake — not here with us –and it all worked out. I’m very happy to be back here on the Croisette.”

Rounding out the cast of “Oh, Canda” are Uma Thurman, Victoria Hill, Michael Imperioli, Penelope Mitchell and Kristine Froseth. Thurman was also on hand for the press conference on Saturday.

77-year-old Schrader has previously been on the Croisette for 1976’s “Taxi Driver,” for which he penned the script. The film went on to win the festival’s prestigious Palme d’Or. His 1985 directorial effort “Mishima: A Life in Four Chapters” premiered in competition at Cannes, and he returned again in 1988 for “Patty Hearst.”

In a recent interview with Variety about “Oh, Canada,” Schrader said making the movie caused him to look back on his own life. “My health hasn’t been good,” he said. “I thought if I wanted to make my death film, it had to be now.”

Gere, who previously worked with Schrader on 1980’s “American Gigolo,” has been at Cannes several times over his decades-long career, including for Akira Kurosawa’s “Rhapsody in August,” which is honored on this year’s official poster for the festival.