Walt Disney World and Disneyland theme parks are introducing demand-based pricing for the first time, raising ticket prices up to 20% for holiday periods and some weekends.

The changes will take effect on Sunday and apply only to single-day tickets, not multi-day packages, the New York Times reports.

At Disneyland in Anaheim, Calif., single-day tickets—which currently cost $99—will now cost $95 on Mondays through Thursdays, $105 on most weekends and many summer weeks, and $119 during peak visit times, including most of December, spring break and July weekends.

At Disney World in Orland, Fla., the changes will vary by park and range from the current price of $105 to $124 for peak visit times.

The demand-based pricing aims to limit crowding and long lines during the holidays, which have become problems at the Magic Kingdom in particular.

“In addition to expanding our parks, we are adopting seasonal pricing on our one-day ticket to help better spread visitation throughout the year,” the company said in a statement, as reported by the Times. “Multiday tickets, annual passes and visiting during nonpeak periods also provide our guests with options and savings.”

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Write to Katie Reilly at Katie.Reilly@time.com.