Can ESXi 5.5 U1 be used with vCenter 5.5 (non-U1)

Hello,

Some of our ESXi 5.5 hosts have been upgraded to U1 but we have not upgrade vCenter to U1 yet.  Is this OK?  My understanding is that vCenter ALWAYS has to be at a higher or same version as the ESXi hosts that it supports.  If this is not OK to do, what kind of problems would be seeing?

Thanks

NK