fastpass doesn't work if vCenter is configured with a domain user

I installed vMA 5.1 with vCenter 5.1.1a.

ssh vi-admin@vma_ip

#vMA has been joined to the AD domain:

vi-admin@vma:~> sudo domainjoin-cli query

vi-admin's password:

Name = vma

Domain = MYDOMAIN.LOCAL

Distinguished Name = CN=VMA,CN=Computers,DC=mydomain,DC=local

ssh MYDOMAIN\\vcenteradmin@vma_ip

vifp addserver testvcenter1.mydomain.local --authpolicy adauth --username MYDOMAIN\\vcenteradmin

vma:~> vifp listservers -l

testvcenter1.mydomain.local     vCenter adauth

esxi-e1b1.mydomain.local        ESXi    adauth

If the target is a ESXi host, fastpass works:

vma:~> vifptarget -s esxi-e1b1.mydomain.local

vma:~[esxi-e1b1.mydomain.local]> esxcli system version get

   Product: VMware ESXi

   Version: 5.1.0

   Build: Releasebuild-1065491

   Update: 1

vma:~[esxi-e1b1.mydomain.local]> vifptarget -c

If the target is the vCenter, fastpass doesn't work:

vma:~> vifptarget -s testvcenter1.mydomain.local

vma:~[testvcenter1.mydomain.local]> esxcli -h esxi-e1b1.mydomain.local system version get

Enter username: MYDOMAIN\vcenteradmin   (<-- credentials required!)

Enter password:

   Product: VMware ESXi

   Version: 5.1.0

   Build: Releasebuild-1065491

   Update: 1

"VMware VirtualCenter Management Webservices" and "VMware VirtualCenter Server" are running with a domain user credentials.

If I set those services to run with LocalSystem user (instead of the domain user), fastpass authentication works flawlessy:

vma:~> vifptarget -s testvcenter1.mydomain.local

vma:~[testvcenter1.mydomain.local]> esxcli -h esxi-e1b1.mydomain.local system version get

   Product: VMware ESXi   (<-- NO credentials required!)

   Version: 5.1.0

   Build: Releasebuild-1065491

   Update: 1

Is that a known bug?