Sprott Physical Silver Trust (PSLV) fell more than silver ETFs on Thursday after its manager announced a follow-on offering to buy more bullion.

Sprott Physical Silver Trust was down 5.4% in premarket trading Thursday.

The iShares Silver Trust (SLV) , an $8.5 billion ETF that invests in silver bullion, slipped 1.5% before the bell.

Sprott Physical Silver Trust fell harder than silver prices because its premium to net asset value narrowed after the follow-on announcement late Wednesday.