[5.3.1p1] WWW.isDone hangs in iOS

It seems that WWW.isDone broke in 5.3.1. This used to work fine in 5.2

This code hangs in iOS:

When running on iOS, the call to www.isDone doesn't return. If I pause the game in XCode, and resume execution.. then it works fine.

Doing the usual yield...

[5.3.1p1] WWW.isDone hangs in iOS