git update-ref fails to create reference. (bug)

While trying to create a pseudo reference named REF pointing to the empty tree iff it doesn't exist, I stumbled on the following:

I assume both are valid ways to create such reference:
 	a) $ echo -e option no-deref\\nupdate REF $(git hash-object -t tree /dev/null) 0000000000000000000000000000000000000000 | git update-ref --stdin
 	b) $ git update-ref --no-deref REF $(git hash-object -t tree /dev/null) 0000000000000000000000000000000000000000

While a) works, b) will throw:
	fatal: could not read ref 'REF'

Bisect seems to point to: 2c3aed138 (pseudoref: check return values from read_ref(), 2015-07-15)

Thanks, Rafael Ascensão