[cisco-voip] CUCM 8.5.1(SU1) phone firmware upgrade procedure

[Hefin James [ahj]]

Hi,
We've recently upgraded to CUCM 8.5.1(SU1) a couple of months ago, and all the 7911's that we have are now running SCCP11.9-1-1SR1S.
However, we had quite a few phone's in storage, and are now rolling these phones out.
These phones (more 7911's) have an old firmware version of SCCP11.8-3-2S, and I need to get them up to version SCCP11.9-1-1SR1S. 
If I try to upgrade them directly, I get Auth-Fail. Does anybody know which interim loads I need to have before I can get from 8-3-2S to 9-1-1SR1S?

Thanks,
Hefin