[libvirt] building error

When I build libvirt, I meet the following error message sometimes: make[4]: Entering directory `/home/wency/rpmbuild/BUILD/libvirt-0.9.11/docs' GEN libvirt-api.xml GEN libvirt-qemu-api.xml GEN html/index.html ./libvirt-api.xml:2450: parser error : AttValue: ' expected <function name='virConnectDomainEventDeregister' file='libvi ^ ./libvirt-api.xml:2450: parser error : attributes construct error <function name='virConnectDomainEventDeregister' file='libvi ^ ./libvirt-api.xml:2450: parser error : Couldn't find end of Start Tag function line 2450 <function name='virConnectDomainEventDeregister' file='libvi ^ ./libvirt-api.xml:2450: parser error : Premature end of data in tag symbols line 1129 <function name='virConnectDomainEventDeregister' file='libvi ^ ./libvirt-api.xml:2450: parser error : Premature end of data in tag api line 2 <function name='virConnectDomainEventDeregister' file='libvi ^ unable to parse ./libvirt-api.xml make[4]: *** [html/index.html] Error 6 make[4]: *** Waiting for unfinished jobs.... If I rebuild it without anything change, the building will success.