[CentOS] Issue with package-cleanup --oldkernels with PAE kernel

I'm not sure if this is a bug, known issue, feature, etc.  On my  
CentOS systems with the PAE kernel installed, package-cleanup behaves  
as follows:

   # rpm -q kernel
   package kernel is not installed
   # rpm -q kernel-PAE
   kernel-PAE-2.6.18-92.1.13.el5
   kernel-PAE-2.6.18-92.1.18.el5
   kernel-PAE-2.6.18-92.1.22.el5
   # uname -r
   2.6.18-92.1.22.el5PAE
   # package-cleanup --oldkernels --count 2
   Setting up yum
   Error all kernel rpms are set to be removed

Has anyone else seen this?  Is this expected behavior or a (known) bug?

Alfred