US officials say an office supply issue was a major reason the African country of Chad was hit with travel restrictions by the United States.

Donald Trump’s administration added Chad in an order last month that a judge put on hold this week. Chad’s inclusion was perplexing because the country cooperates closely with the US on counter-terrorism.

It turns out a seemingly pedestrian issue was to blame: Chad ran out of passport paper.

All countries had been given 50 days to take several steps that included providing a recent passport sample. Chad couldn’t comply, and its offer to provide a pre-existing sample wasn’t sufficient.

The homeland security department says there were other reasons Chad was added, too. The department says the US is working with Chad to resolve them.