Distributed Cache Instance Role Support

Does the distributed cache feature support using Amazon Instance Roles to obtain credentials? I tried configuring a runner with the access/secret key blank like some of the other AWS integrations but my cache doesn't seem to be working. The only error I found is the following, which seems to imply it doesn't support this:

Sep 23 00:22:34 ip-10-78-7-226 gitlab-runner[10678]: #033[34mINFO#033[0m[6690] Starting docker-machine build...              #033[34mbuild#033[0m=13 #033[34mcreated#033[0m=2016-09-22 23:54:43.676633781 +0000 UTC #033[34mdocker#033[0m=tcp://10.78.4.103:2376 #033[34mname#033[0m=runner-105a46c2-autoscale-us-west-21474588483-72a7f7d2 #033[34mnow#033[0m=2016-09-23 00:22:34.463239321 +0000 UTC #033[34mproject#033[0m=23 #033[34mrunner#033[0m=105a46c2 #033[34musedcount#033[0m=5#012<nil>
Sep 23 00:22:36 ip-10-78-7-226 gitlab-runner[10678]: #033[33mWARN#033[0m[6691] Requests cannot be presigned with anonymous credentials. #012<nil>
Sep 23 00:22:59 ip-10-78-7-226 gitlab-runner[10678]: #033[33mWARN#033[0m[6714] Requests cannot be presigned with anonymous credentials. #012<nil>
Sep 23 00:23:00 ip-10-78-7-226 gitlab-runner[10678]: #033[34mINFO#033[0m[6716] Finished docker-machine build: <nil>          #033[34mbuild#033[0m=13 #033[34mcreated#033[0m=2016-09-22 23:54:43.676633781 +0000 UTC #033[34mdocker#033[0m=tcp://10.78.4.103:2376 #033[34mname#033[0m=runner-105a46c2-autoscale-us-west-21474588483-72a7f7d2 #033[34mnow#033[0m=2016-09-23 00:23:00.775908398 +0000 UTC #033[34mproject#033[0m=23 #033[34mrunner#033[0m=105a46c2 #033[34musedcount#033[0m=5#012<nil>

If it is supported, any info on how? I can submit a change to the docs to reflect it.