The slight premium in an exchange traded note indexed to master limited partnerships is a reminder that investors need to be on guard when products halt the creation of new shares.

JPMorgan Alerian MLP Index ETN (NYSEArca: AMJ) was trading at a premium of about 1% to indicative value on Tuesday.

The $5 billion ETN recently reached the limit on the number of shares outstanding set by issuer JP Morgan (NYSE: JPM).

In terms of inflows, AMJ may have had its “last hurrah” in June, says investment researcher Morningstar.

“It saw a $574 million inflow, but the bank has halted new share creations given the difficulty in hedging out MLP exposure,” Morningstar said. The premium recently rose to nearly 3% and any new investor interest in the ETN may increase the premium, it added.

Exchange traded products essentially turn into closed-end funds when the manager suspends the creation of new shares. As a result, premiums and discounts to net asset value can materialize.

For example, VelocityShares Daily 2X VIX Short-Term ETN (NYSEArca: TVIX) quickly lost 50% of its value earlier this year when its premium collapsed. TVIX issuer Credit Suisse in February suspended the creation of new shares due to size limits. [MLP ETN Hits Size Limit, Premium May Follow]