PHOTOSHOP CS6: Can't save animated gif without changing background to transparent

Not sure if this was fixed in CC:
I'm using Photoshop CS6 and I just noticed that if you open animated gif, edit it and try to 'Save for Web...' the white background will always turn to transparent whatever option you check. I had to remake my gif from the scratch so the background stays white as it was from the beginning.

I'm using Windows 7 64bit,
full action order: Open (animated gif), Rotate Canvas (I had to rotate my gif 90 degree), Save for Web...