Microsoft announced some new location targeting changes that it’s getting ready to implement in adCenter, which provides the ads on not only Bing, but Yahoo in an increasing number of countries.

The changes are only coming to the U.S. and Canada for now, however. Microsoft is removing about 10,000 cities from adCenter targeting, starting in mid to late May.

“Because these cities have seen no measurable traffic, this change will have no negative impact on the performance of your campaigns,” says Microsoft’s Peter Yang. “If you are targeting a city that will be removed, we recommend that you update your settings to target a city supported by adCenter to gain more traffic.”

Microsoft provides a downloadable spreadsheet, where you can see all of the locations that are going away, and their corresponding locations that you should be targeting. Find the ones you need to be targeting, then simply go into adCenter and replace the non-supported ones with the corresponding supported ones.

Microsoft will pause any campaigns or ad groups that only target cities that are being removed. The default target will be set to worldwide. In other words, this probably isn’t something you want to ignore. If some supported cities are sprinkled in, those cities will still be targeted. If you’re using the API to call non-supported cities, an error message will appear.

If you think that losing some of these cities will hurt your campaign, Microsoft aims to convince you otherwise. The company says you are likely to see an increase in impressions (though you probably know your campaign better than anyone, and it might depend on your reasons for targeting select cities).