Items in chest disappear when opening world in prior version (1.7.9

Create new world in 14w21b, create several chests, put something in each one.
Open world in 1.7.9 and save.
Re-open world in 14w21b. Chest items are gone.

Issue does not happen to worlds created in 1.7.9 and opened in 14w21b as far as my testing has gone.