The fortunately temporary expiration of the federal terrorism insurance backstop came as a year-end drama that supporters of the program certainly could have lived without.

Admittedly, the circumstances that led to the lapse were unusual and unlikely to be repeated when the program comes up for renewal at the end of 2020. One retiring senator objected to a provision creating a new National Association of Registered Agents and Brokers, a provision no one else found objectionable, and managed to block the lame-duck Senate from passing a House-approved extension bill. That lawmaker — Sen. Tom Coburn, R-Okla. — is now gone from Washington.

Even the barely week-long lapse of the federal terrorism program had market implications, as we report elsewhere in this issue. Insurers had to get reinsurance they otherwise wouldn't have needed; some businesses had to scramble for coverage amid market uncertainty.

Now that the uncertainty's been lifted, it's not too soon for advocates of the program to start considering how to avoid another lapse.

We think the best way is to make the program permanent.

The reason for establishing the program, which was created by the Terrorism Risk Insurance Act of 2002, was to allow the creation of a private terrorism insurance market. That market is emerging more slowly than expected, and for good reason. Unlike natural risks, the man-made risk of terrorism defies normal underwriting practices. As the world learned all too tragically again in Paris a few days ago, terrorist attacks ignore prediction.

Putting the program on a permanent footing might require some structural changes. Insurers, who will assume a greater share of any future terrorist losses under the measure just signed into law, may have to accept an even larger share. In fact, the price could ultimately be a requirement that insurers — and indirectly their policyholders — pay some small premium upfront to help prepay for the program.

Supporters of the program have nearly six years to consider what needs to be done to make the backstop permanent. They should make the best use of that time, too. In an ever-more-dangerous world, even another short-term lapse is a risk we can ill afford to take.