Docker Size and VirtualSize reported differently on v1.9 and v1.10

docker110

$ docker version
Client:
 Version:      1.10.1
 API version:  1.22
 Go version:   go1.5.3
 Git commit:   9e83765
 Built:        Thu Feb 11 19:27:08 2016
 OS/Arch:      linux/amd64

Server:
 Version:      1.10.1
 API version:  1.22
 Go version:   go1.5.3
 Git commit:   9e83765
 Built:        Thu Feb 11 19:27:08 2016
 OS/Arch:      linux/amd64
$ docker build -t newimage .
Sending build context to Docker daemon  2.56 kB
Step 1 : FROM alpine
 ---> 70c557e50ed6
Step 2 : LABEL FOO Bar
 ---> Running in 2ee44a845a12
 ---> 68b00a004e35
Removing intermediate container 2ee44a845a12
Successfully built 68b00a004e35
$ docker run -v /var/run/docker.sock:/var/run/docker.sock nate/dockviz images --incremental --tree alpine
└─sha256:70c55 Virtual Size: 4.8 MB Tags: alpine:latest
  └─sha256:68b00 Virtual Size: 4.8 MB Tags: newimage:latest
[
  {
    "Id": "sha256:68b00a004e355c630bce05c703d5972490d38a3e9bc2e24ef1861a724166bd1c",
    "ParentId": "sha256:70c557e50ed630deed07cbb0dc4d28aa0f2a485cf7af124cc48f06bce83f784b",
    "RepoTags": [
      "newimage:latest"
    ],
    "RepoDigests": null,
    "Created": 1458227249,
    "Size": 4797951,
    "VirtualSize": 4797951,
    "Labels": {
      "FOO": "Bar"
    }
  }
]

docker19

$ docker version
Client:
 Version:      1.9.1
 API version:  1.21
 Go version:   go1.4.3
 Git commit:   a34a1d5
 Built:        Fri Nov 20 17:56:04 UTC 2015
 OS/Arch:      linux/amd64

Server:
 Version:      1.9.1
 API version:  1.21
 Go version:   go1.4.3
 Git commit:   a34a1d5
 Built:        Fri Nov 20 17:56:04 UTC 2015
 OS/Arch:      linux/amd64
$ docker build -t newimage .                                                                                                                                                                                      
Sending build context to Docker daemon  2.56 kB
Step 1 : FROM alpine
 ---> 9a686d8dd34c
Step 2 : LABEL FOO Bar
 ---> Running in 675db9644411
 ---> 28c756c523fc
Removing intermediate container 675db9644411
Successfully built 28c756c523fc
$ docker run -v /var/run/docker.sock:/var/run/docker.sock nate/dockviz images --incremental --tree alpine                                                                               
└─9a686d8dd34c Virtual Size: 4.8 MB Tags: alpine:latest
  └─28c756c523fc Virtual Size: 0.0 B Tags: newimage:latest
$ echo -e "GET /images/json?all=1 HTTP/1.0\r\n" | nc -U /var/run/docker.sock | tail -n 1 | jq '. | map(select(.RepoTags[] | contains ("newimage:latest")))'
[
  {
    "Id": "28c756c523fca866d4b15ef62fe70c6b4f1ad95bfa45f2c54070b9fb129ad64b",
    "ParentId": "9a686d8dd34c0a9d62c9f4df0347096ab3babe858e40a29c144d2033b63a33eb",
    "RepoTags": [
      "newimage:latest"
    ],
    "RepoDigests": [],
    "Created": 1458227155,
    "Size": 0,
    "VirtualSize": 4797951,
    "Labels": {
      "FOO": "Bar"
    }
  }
]

Dockerfile

FROM alpine
LABEL FOO=Bar