The Canadian government is officially warning travellers that they could face problems entering the U.S. if they have an “X” gender marker on their passport.

Global Affairs Canada recently added an advisory to its U.S. travel advice page, stating that travellers with an “X” marker could face restrictions in places that “do not recognize” the gender marker, like the U.S.

In addition, the new notice warns that Canadians with an “X” on their passport might be asked to provide documentation of one’s sex as male or female when travelling to prevent any issues.

The updated language comes after it was reported that Canadian government officials discussed issuing a travel advisory for trans travellers going to the U.S. in the days following Trump’s executive order mandating that all government documents reflect a person’s sex at birth. But it didn’t publish any official guidance until now.

It’s currently unclear why the guidance was changed now rather than when the executive order was signed, or how many, if any, Canadian travellers have been impacted so far. Jennifer Young, a spokesperson for the U.S. Embassy in Canada, told the CBC that the delegation was not able to provide further comment due to the current government shutdown in the U.S.

The “X” designation has been available to Canadian travellers since 2017. Back in January, the government said roughly 3,600 citizens adopted the “X” marker on their passports.