It took Ms Catherine Chong five minutes to get a trolley when she went shopping at Cold Storage recently. That was because the new dollar coin she was using did not fit.
"Perhaps there should be signs reminding customers," said the civil servant, 29.
This is one example of how the new series of coins launched on June 25 has been causing some confusion among consumers.
The problem is not widespread, with only six out of the 20 people polled by The Straits Times saying they have used the new coins.
But it also did not help that the new 50 cent and old 20 cent coins are similar in size and weight, said shopkeepers.
Said provision shop owner Ken Ong, 31: "A customer thought I was short-changing her when she mistook the new 50 cent coin for the old 20 cent one."
Banks currently issue both the new and old coins depending on stocks in their coffers. Despite the launch of Singapore's third series of coins, the previous series remains legal tender, said the Monetary Authority of Singapore.
Supermarkets are already trying to accommodate the new coins. From September, Giant and Cold Storage trolleys will be refitted with new locks that accept both new and old $1 coins. Until then, these stores will put up signs telling customers that they can change their new dollar coins for the old ones at counters, a spokesman said.
NTUC FairPrice customers will be able to use new 50-cent coins on its trolleys, which currently also accepts old $1 coins. The coins share similar dimensions.
Signs will also be put up at trolley points informing shoppers of the option, its spokesman said.
Despite some of the hassle, Singapore's third series of coins has its fans.
"The new coins are well designed with Singapore landmarks on them," said project manager Nelson Hiang, 35, who exchanged his notes for $80 worth of new $1 coins once they were available.