The U.S. Securities and Exchange Commission (SEC) rejected Wilshire Phoenix’s bid for a bitcoin-based exchange-traded fund (ETF).

In a filing posted Wednesday, the securities regulator wrote the New York-based Wilshire Phoenix had not proven the bitcoin (BTC) market is sufficiently resistant to market manipulation. Wilshire, a newcomer to the financial services industry, first applied for the ETF last summer with NYSE Arca.

“The Commission concludes that NYSE Arca has not met its burden under the Exchange Act and the Commission’s Rules of Practice to demonstrate that its proposal is consistent with the requirements of Exchange Act Section 6(b)(5), and, in particular, the requirement that the rules of a national securities exchange be ‘designed to prevent fraudulent and manipulative acts and practices’ and ‘to protect investors and the public interest,'” the filing said.

SEC Commissioner Hester Peirce, known as “crypto mom” in the space, published a dissent, writing that the agency applies a “heightened standard” to bitcoin products. As an example, she said the SEC had not required surveillance-sharing agreements with markets of significant size, an argument the agency outlined in its rejection of Bitwise’s bitcoin ETF application.

“This line of disapprovals leads me to conclude that this Commission is unwilling to approve the listing of any product that would provide access to the market for bitcoin and that no filing will meet the ever-shifting standards that this Commission insists on applying to bitcoin-related products—and only to bitcoin-related products,” she wrote.

The SEC has rejected all previous bitcoin ETF proposals filed to date. Wilshire hoped to buck the trend by basing its ETF proposal on U.S. Treasury bonds in addition to bitcoin. William Herrmann, Wilshire’s managing director, previously told CoinDesk the fund would automatically rebalance itself in response to bitcoin’s price volatility. Should the cryptocurrency’s price fluctuate too much, the fund would invest more heavily into bonds, and reverse that position as the price stabilizes.

This automatic rebalancing came as a response to the SEC’s previous rejections. The agency rejected a number of bitcoin ETF applications out of concerns the bitcoin market is not significant in size and potentially easy to manipulate.

Last year, the agency published a rejection order for Bitwise Asset Management’s bitcoin ETF proposal on these grounds.

UPDATE (Feb. 26, 22:46 UTC): This article has been updated with SEC Commissioner Hester Peirce’s dissent, published Wednesday.