The kernel included in RHEL 5.2 and thus also in Centos 5.2 backported a feature from kernel 2.6.19: the type "bool". The xpp driver used a "bool" type of its own even before definition. Hence it only adds that typedef for kernel versions that should not have it already: kernel/xpp/xdefs.h: #if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,19) typedef int bool; #endif Thus we get the following error: CC