Canadians have been paying tribute to the late actor Leonard Nimoy in a somewhat unusual way: By defacing their currency.

The old Canadian five-dollar bill shows the image of former Prime Minister Sir Wilfrid Laurier, whose chiseled face and blue suit bear a striking resemblance to that of Star Trek character Mr. Spock as portrayed by Nimoy.

As such, some Canadians have been altering the five-dollar bill for the past several years — a practice known as “Spocking.” Though the hobby has been around since at least 2009, it has received renewed attention following Nimoy’s death last Friday.

Canada switched from paper to plastic currency two years ago, although some paper five-dollar notes can still be found in circulation. While defacing Canadian currency isn’t a crime, it is strongly discouraged by government officials. A spokesperson for the Bank of Canada told the website Quartz on Monday that altering the currency “may interfere with the security features and reduces its lifespan,” and marking banknotes “may also prevent it from being accepted in a transaction.”

In other words, defaced Canadian banknotes may not live very long, and those who alter them might not prosper.