Target has made a $75 million minority investment in Casper Sleep, the leader in the direct “bed in a box” mattress market. The investment, first reported by Recode, comes after Target reportedly offered $1 billion to acquire the upstart.

Known for its foam mattresses folded into ultra-compact packages for shipping, Casper was valued at $550 million in its last private equity funding in 2015 and is said to be eyeing an IPO. Competitors such as Leesa, Tuft & Needle and Purple are expanding, but haven’t received significant funding. More traditional mattress companies are expected to enter the category in the coming year.

On May 16, Target revealed a partnership that lets its customers buy beds and accessories from Casper. That rollout begins on June 18.

“Target invested in Casper because we believe in their team, their ideas and their vision…