helm: --reuse-values does not work as expected with requirements conditions

helm version
Client: &version.Version{SemVer:"v2.6.1", GitCommit:"bbc1f71dc03afc5f00c6ac84b9308f8ecb4f39ac", GitTreeState:"clean"}
Server: &version.Version{SemVer:"v2.6.1", GitCommit:"bbc1f71dc03afc5f00c6ac84b9308f8ecb4f39ac", GitTreeState:"clean"}

What happened:

I have a simple chart with a subchart installed. In the requirements.yaml I have condition: subchart.enabled

Check out my gist of the the chart including bug-example-0-1-0-tgz:

helm install . --set subchart.enabled=true --set subchart.hello=Subchart --set hello=World 
NAME:   alternating-stingray
LAST DEPLOYED: Mon Sep 18 11:22:13 2017
NAMESPACE: default
STATUS: DEPLOYED

RESOURCES:
==> v1/ConfigMap
NAME                                  DATA  AGE
subchart-config-alternating-stingray  1     0s
chart-config-alternating-stingray     1     0s

I see both the subchart and chart are installed. Now when I upgrade with --reuse-values I see that my subchart template is not included:

(srossross-mac bug-example •‿•) helm upgrade alternating-stingray . --reuse-values --debug --dry-run
[debug] Created tunnel using local port: '63488'

[debug] SERVER: "localhost:63488"

REVISION: 2
RELEASED: Mon Sep 18 11:27:28 2017
CHART: bug-example-0.1.0
USER-SUPPLIED VALUES:
{}

COMPUTED VALUES:
hello: World
subchart:
  enabled: true
  global: {}
  hello: Subchart

HOOKS:
MANIFEST:

---
# Source: bug-example/templates/configmap.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: chart-config-alternating-stingray
data:
  hello: World
Release "alternating-stingray" has been upgraded. Happy Helming!
LAST DEPLOYED: Mon Sep 18 11:22:13 2017
NAMESPACE: default
STATUS: DEPLOYED

RESOURCES:
==> v1/ConfigMap
NAME                                  DATA  AGE
subchart-config-alternating-stingray  1     5m
chart-config-alternating-stingray     1     5m

What you expected to happen:

The subchart is included in the upgrade.