cache.get() only works for the first call

I'm using 2.4-m1.  
The previously working code to set non-expiring cache:  `Cache.set("tags", Set("a", "b", "c"))`, doesn't work any more. The default `expiration = 0` which is supposed to mean eternity, now only setting the cache for once, it seems to work for other values, but not 0.