Apple’s new headquarters features numerous interior walls and doors made from glass. Unfortunately the seemingly obvious has happened.

Apple Park took four years to build and reportedly cost more than $5 billion. Designed by famed architect Norman Foster, it followed on from the instructions of the late Steve Jobs who wanted a way to keep the entire company’s HQ under a single roof. The circular building would fit almost perfectly on top of the Pentagon.

As well as large parts of the building exterior being made of curved glass, much of the internal work spaces have glass walls and doors, giving a mix of private space and open plan design. Documents obtained by Marketwatch under public records requests show at least two staff have required emergency service attention after walking into the glass. The request follows Twitter posts by staff suggesting seven people hurt themselves on the day the new facility opened to employees.

TIME believes the mishaps aren’t entirely down to the glass design but also the fact that, as you might expect, Apple staff tend to walk around while engrossed in their iPhone displays. The magazine even claims some staff used Post-It notes to make the walls more visible only for them to be removed for spoiling the visual effect.

While hopefully staff have got to grip with the design now, let’s hope the building doesn’t turn into a greenhouse in the summer when average temperatures in the area approach 30 degrees Celsius.