....'please close all window shades immediately'

34,000 feet, polar route, I was dozing and I thought that I misheard the German announcement initially, but passengers suddenly scrambled to comply. I then listened to the announcement in English but the person making the announcment (purser, I believe) had quite poor English (not Germisch!) that I wasn't sure if he said that in English.

Has anyone had that experience? I have never heard that request before in my flying history and found it unusual.