It’s enough to melt even the toughest soldier’s heart.

One of the British Queen’s Coldstream Guards spotted little birthday boy Marshall Scott wearing a replica uniform and saluting his unit during the “Changing the Guard” ceremony outside Windsor Castle on Wednesday. So he marched back and beckoned him over so they could pose for a photograph.

Instagram user joanna___feng shared footage of the heartwarming moment online. One of the guardsmen re-shared it and it’s since gone viral.

#windsorcastle 萌吐奶 A video posted by Jie Feng (@joanna___feng) on Jan 4, 2017 at 10:03am PST

“It’s not the usual thing to happen while on guard,” admitted Lance Corporal Paul Edden, the guardsman who broke with convention to perform the inspiring act for Marshall who turned 4 on the day.

“Usually I would just take the guardsmen in the guardroom as normal, but my wife and I are expecting a baby boy, and I remembered standing at Edinburgh Castle when I was young hoping to get a picture with a soldier,” Edden told London’s Evening Standard newspaper. “I noticed Marshall in a Coldstream guards uniform, and seeing him coming out made me proud of what I do.”

Imogen Scott, Marshall’s mom, revealed the moment had left her feeling “overwhelmed.” “He is so happy,” she said of her son. “Literally his dreams have come true.”

A group of girls had also sung “Happy Birthday” to Marshall and a family had bought him a soldier teddy bear, she said. And Edden has invited them for a tour of the castle ― which is one of Queen Elizabeth II’s official residences.