Last week, parts of Apple’s new flagship retail store in Chicago had to be roped off, as dangerous icicles started to form on the roof. Although many believed the design of the MacBook Air-like roof was flawed, Apple later explained that the problem was instead a software issue that caused its heating system to break.

Apple spokesman Nick Leahy told The Chicago Tribune last week that the building’s architects, from the London-based Foster+Partners, had designed the store to be snow-friendly. “The roof has a warming system that’s built into it,” said Leahy. “It needed some fine-tuning and it got reprogrammed today. It’s hopefully a temporary problem.”

After the ice melts through Apple’s heating system, the water was supposed to be drained through four internal support columns, instead of through the gutter like buildings normally do. Back when the Chicago flagship was first unveiled in October last year, people marveled not only at its shiny physical appearance but also at its heating and cooling system that involves pumping water from the river to stay green.