Paul Schrader had a special task on the set of his latest film, “Oh, Canada”: taking inspiration from the jockstrap worn by Jacob Elordi in one of the pivotal scenes of the Vietnam War drama.

There’s a choice at the heart of “Oh, Canada,” when fictional filmmaker Leonard Fife (played as a young man by Elordi and as an older man as Richard Gere) avoids the Vietnam draft and fled to Canada. The script leaves a breadcrumb trail of what exactly is happening until very late in the film, but eventually we see Elordi reporting for an army medical exam. He presents himself in a jockstrap with “peace and love” written on the jockstrap, surrounded by small flowers. He trembles, trembles and waves his arms flamboyantly. In character, Elordi tries to appear as unstable (and, frankly, homosexual) as possible to avoid enlisting in military service.

During the film’s press conference at the Cannes Film Festival, Schrader revealed that he added finishing touches to the jockstrap Elordi’s character wears during the scene.

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

Schrader reflected on a “two to three year period where all young Americans had to make a decision” regarding the draft. Schrader said he was discharged from service for medical reasons. His friends were drafted and others wandered across the country to escape Uncle Sam. He even shouted “Oliver Stone, who went to Vietnam and won an Oscar.” Indeed, Stone served in the 1960s and was twice wounded in combat.

Schrader’s latest film was screened Friday night to a four-minute standing ovation, even though Elordi was absent because he was filming Guillermo del Toro’s “Frankenstein.” Once the ovation was over, Schrader addressed Elordi who was not there, saying: “I’m very happy with Richard, Uma, Jake – not here with us – and everything went well. I am very happy to be back here on the Croisette.

The cast of “Oh, Canda” is completed by Uma Thurman, Victoria Hill, Michael Imperioli, Penelope Mitchell and Kristine Froseth. Thurman was also present for Saturday’s press conference.

Schrader, 77, had previously appeared on the Croisette for the 1976 film “Taxi Driver,” for which he wrote the screenplay. The film went on to win the festival’s prestigious Palme d’Or. His 1985 film “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 Of “Oh, Canada,” Schrader said making the film made him look back on his own life. “My health is not good,” he said. “I thought if I was going to make my death movie, it had to be now.”

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