Animated GIF shared to Twitter doesn't animate.

I'm creating an animated GIF in my app, but when I post it using `UIActivityViewController`, it isn't animated. The same is true if I save the GIF to the photo library and post it from there. However, if I delete the official Twitter app and then share it using either of the aforementioned methods, then it works fine. It seems crazy that the Twitter app has special access to somehow break system functionality. Is there a way round this? Perhaps something I can specify in the file's metadata, or another way to share it to Twitter? Thanks.