ENTRYPOINT [] not resetting parent image entrypoint

[md5]

According to the discussion in the comments of #3465, using ENTRYPOINT [] should be a way to remove the entrypoint setting from a parent image. However, this doesn't seem to be the case:

$ { echo 'FROM busybox'; echo 'ENTRYPOINT ["/bin/true"]'; } | docker build -t test-entrypoint-1 - 
Sending build context to Docker daemon 2.048 kB
Sending build context to Docker daemon 
Step 0 : FROM busybox
 ---> e72ac664f4f0
Step 1 : ENTRYPOINT /bin/true
 ---> Using cache
 ---> c55134211aec
Successfully built c55134211aec
$ { echo 'FROM test-entrypoint-1'; echo 'ENTRYPOINT []'; } | docker build -t test-entrypoint-2 - 
Sending build context to Docker daemon 2.048 kB
Sending build context to Docker daemon 
Step 0 : FROM test-entrypoint-1
 ---> c55134211aec
Step 1 : ENTRYPOINT
 ---> Running in 52e236ac9ed7
 ---> e5ab1267141c
Removing intermediate container 52e236ac9ed7
Successfully built e5ab1267141c
$ docker inspect -f '{{.Config.Entrypoint}}' test-entrypoint-2
[/bin/true]
$ docker version
Client version: 1.3.0
Client API version: 1.15
Go version (client): go1.3.3
Git commit (client): c78088f
OS/Arch (client): darwin/amd64
Server version: 1.3.0
Server API version: 1.15
Go version (server): go1.3.3
Git commit (server): c78088f

[md5]

In particular, @tianon's comment here.