Centos Kickstart - partitioning fails because of arbitrary disk order

I've prepared a kickstart file for a Red Hat Virtualization 4.4 VM with 3 virtio-scsi disks with different disk sizes:

# System bootloader configuration
bootloader --append=" crashkernel=auto" --location=mbr --boot-drive=sda

# Partition clearing information
clearpart --all --initlabel --drives=sda,sdb,sdc

reqpart --add-boot

# Disk partitioning information
part /boot --fstype="xfs" --ondisk=sda --size=500


part pv.192 --fstype="lvmpv" --ondisk=sda --size=1 --grow
volgroup centos --pesize=4096 pv.192
logvol / --fstype="xfs" --size=12336 --maxsize=12336 --grow --name=root --vgname=centos
logvol swap --fstype="swap" --size=2048 --name=swap --vgname=centos

part pv.193  --fstype="lvmpv" --ondisk=sdb --size=1 --grow
volgroup logs --pesize=4096 pv.193
logvol /var/log  --fstype="xfs" --maxsize=10240 --size=4096 --grow  --name=log --vgname=logs

part pv.194 --fstype="lvmpv" --ondisk=sdc --size=25000 --grow
volgroup app --pesize=4096 pv.194
logvol /opt --fstype="xfs" --size=25000 --maxsize=25000 --grow --name=app --vgname=liberty

Problem during installation:

Storage configuration failed: Unable to allocate requested partition scheme.

A quick view into lsblk and /dev/disk/by-id shows that the ordering of the disks is wrong or even arbitrary:

scsi-0QEMU....... -> ../../sdc
scsi-0QEMU....... -> ../../sda
scsi-0QEMU....... -> ../../sdb

sda has 12 GB

sdb has 25 GB

sdc has 15 GB

Any glues on this?