As a 1969 SFU graduate, Margaret Trudeau was one of five graduates receiving the university's outstanding alumni award Thursday night at the Vancouver Convention Centre.

Trudeau was recognized for her work advocating for mental health. 

And while she knew she was getting an award, she had no idea there would be a special guest at the ceremony — her son, Prime Minister Justin Trudeau — who started his speech by saying, until recently people had always approached him to praise his father.

'Merci maman,' says Justin Trudeau1:32

"But I have to say over the past five years or so, as many people have been coming up to me to tell me the extraordinary impact my mom has had," he told the crowd.

Justin Trudeau was in Vancouver for Thursday's First Ministers' Conference, but Margaret Trudeau says SFU still managed to keep it a secret that her son would be there to celebrate her award. 

"I saw the card on the chair beside mine that said honorary guest," she said. 

Margaret and Justin Trudeau

Big hug of congratulations for mom. (Lien Yeung/CBC)

"I asked who is that? They said maybe the governor general," she laughed.

Justin Trudeau's speech about his mother brought tears to the eyes of many in the crowd.

"I am incredibly proud to be my mother's son and I don't care who knows it," he told the crowd. "I am who I am because of my mother."

"Merci maman, merci." 

Justin Trudeau

"I am incredibly proud and I don't care who knows it," said Trudeau. "Merci maman, merci."

With files from Deborah Goble