The change, apparently made just before this weekend, means that the scores of people who had previously been turned away from the ride because they were too large for safety devices can now enjoy it.
"Ever since it opened, there has been some discussion about how people couldn't ride," said Matt Roseboom, editor-in-chief of Orlando Attractions Magazine, which published a first-hand account of the change Saturday.
Roseboom said that since the ride opened in May, many guests complained they couldn't ride because their safety restraints wouldn't fully close. It was the only ride at Universal they apparently couldn't fit.
(The Harry Potter ride technically isn't a roller coaster but a simulator that travels on a track.)
Universal had installed special test seats at the entrance to the ride so larger patrons didn't need to wait on an hours-long line only to discover that they didn't fit. A green light and you were good to go. A red one meant no luck until you shed a few pounds. Roseboom said those test seats now also have a yellow light directing passengers to a special few seats with modified restraining devices.
Instead of hundreds of guests being turned away each day, Roseboom said, attendants told him only one was rejected in two days.
Universal acknowledges the change but isn't saying much.
"We routinely make minor adjustments to new attractions after having the opportunity to watch them operate, but we don't generally discuss the details of those adjustments," Tom Schroder, a spokesman for Universal Orlando said in an e-mail to ABC News.
The park tries to accommodate as many guests as possible on its rides, and after watching "Harry Potter" operate for several months, Schroder said, "we made some adjustments to the ride's overhead restraint system that would allow more people to ride."
"We're thrilled to be able to give more people the opportunity to experience this attraction," he said.
Universal isn't alone in facing a -- literally -- growing problem. As America's waistline expands, amusement parks and their customers are looking for ways to adapt. Parks have to balance safety against the risk of alienating paying guests. Larger guests simply want to take the same rides as their skinner friends.
Adult men and women are about 25 pounds heavier than they were in 1960, and 65 percent are considered overweight, according to the National Center for Health Statistics. The average weight for men jumped from 166 pounds in 1960 to 191 pounds in 2002; women average 164 pounds instead of 140.
When Angel Pillow went on a family vacation to Cedar Point amusement park in Sandusky, Ohio a few summers ago, riding the roller coasters was one of the highlights for her husband and children.
But for Pillow, who weighed 240 pounds at the time, there was no joy, just humiliation. She waited more than an hour in line to ride Millennium Force, but when she tried to squeeze into a seat, her weight got in the way.