Once the domain of grandmothers in their tatami-matted living rooms, "granny hobbies" have been picking up steam with Japanese youth.

The latest victim of the trend? Yarn shortages. Gosho, a yarn manufacturer, took to its X account on Feb. 19 to warn customers it couldn’t guarantee product quality if bought from online resellers — because teens and 20-somethings are out here buying up yarn like it’s the new Bitcoin.

Since autumn, crocheting and knitting have been having a moment. Hobbyists have therefore been met with empty shelves at 100-yen shops, leading desperate crafters to turn to resale sites where yarn is fetching higher prices.