Agent Side Checkout fails (Linux) - Perforce password (P4PASSWD) invalid or unset

Using Team City 2017.1

I am unable to use Agent Side checkout with my Ubuntu 14.04 build agent due to the following error:

[2017-06-22 13:41:12,779] INFO - jetbrains.buildServer.VCS.P4 - Running p4 login for user myUserId in [P4Port: redacted-server-address:1666; P4User: myUserId; perforce client mapping with 1 rules, VCSRoot: "ETG" {internal id=170}]
 [2017-06-22 14:07:38,029] INFO - jetbrains.buildServer.VCS.P4 - Creating P4 workspace TC_p4_LinuxBuildAgent1_964e0a7b4154cd8c_85d77afe3e61a99a
 [2017-06-22 14:07:38,225] INFO - jetbrains.buildServer.VCS.P4 - Creating/updating Perforce client specification:
 Client: TC_p4_LinuxBuildAgent1_964e0a7b4154cd8c_85d77afe3e61a99a
 Owner: myUserId
 Description:
 Created by TeamCity for user myUserId.
 Root: /home/someuser/BuildAgent/work/964e0a7b4154cd8c
 Options: noallwrite clobber nocompress unlocked nomodtime rmdir
 Host: ubuntu
 SubmitOptions: revertunchanged
 LineEnd: local
 
 View:
 
 //ETS/GE_DEV/Build/... //TC_p4_LinuxBuildAgent1_964e0a7b4154cd8c_85d77afe3e61a99a/...
 
 [2017-06-22 14:07:38,436] INFO - jetbrains.buildServer.VCS.P4 - Running p4 login for user myUserId in [P4Port: redacted-server-address:1666; P4User: myUserId; perforce client mapping with 1 rules, VCSRoot: "ETG" {internal id=170}]
 [2017-06-22 14:07:39,016] WARN - l.patch.AbstractSourcesUpdater - Error while checkout on agent: Perforce password (P4PASSWD) invalid or unset. - while running 'p4 -c TC_p4_LinuxBuildAgent1_964e0a7b4154cd8c_85d77afe3e61a99a -u myUserId -p
 redacted-server-address:1666 -H ubuntu client -i'
 jetbrains.buildServer.vcs.VcsException: Perforce password (P4PASSWD) invalid or unset. - while running 'p4 -c TC_p4_LinuxBuildAgent1_964e0a7b4154cd8c_85d77afe3e61a99a -u myUserId -p redacted-server-address:1666 -H ubuntu client -i'
 at jetbrains.buildServer.vcs.perforce.PerforceConnection.runCommand(PerforceConnection.java:271)
 at jetbrains.buildServer.vcs.perforce.PerforceConnection.runCommand(PerforceConnection.java:257)
 at jetbrains.buildServer.vcs.perforce.PerforceWorkspacesImpl.createOrUpdateWorkspace(PerforceWorkspacesImpl.java:80)
 at jetbrains.buildServer.vcs.perforce.PerforceAgentSourceUpdater.createOrUpdateLocalWorkspace(PerforceAgentSourceUpdater.java:99)
 at jetbrains.buildServer.vcs.perforce.PerforceAgentSourceUpdater.updateSources(PerforceAgentSourceUpdater.java:68)
 at jetbrains.buildServer.vcs.perforce.PerforceAgentSourceUpdater.updatePerforceSources(PerforceAgentSourceUpdater.java:55)
 at jetbrains.buildServer.vcs.perforce.PerforceSourceUpdatePolicy.updateSources(PerforceSourceUpdatePolicy.java:66)
 at jetbrains.buildServer.agent.impl.vcs.AgentVcsManagerExImpl$CheckoutSupportImpl.updateSources(AgentVcsManagerExImpl.java:108)
 at jetbrains.buildServer.agent.impl.patch.ProjectSourcesOnAgent$1.run(ProjectSourcesOnAgent.java:186)
 at java.lang.Thread.run(Thread.java:745)

I am fairly certain our Perforce server uses ticket based auth. At the build machine, I can run p4 login (which prompts for password). This is successful and allows me to run p4 client which returns a User specification that includes an "AuthMethod: perforce" (the user specification does not include a "Password:" line).

I have tried a couple of different workarounds including:

- Creating a .p4enviro file which includes the P4PASSWD
- Setting an environment variable for P4PASSWD (in /etc/environment)

However, these have no effect...

The logs seems strange to me because the login appears to succeed (at least, no errors are logged). But, the checkout fails with the P4PASSWD error.

Also, the VCS root is using a Client mapping (but I have tried it with Client as well - same error is present).

Any help would be very appreciated!