yum updateで/bootの容量が足りない

yum updateでエラー

Transaction Check Error:
  installing package kernel-2.6.32-431.3.1.el6.x86_64 needs 12MB on the /boot filesystem

Error Summary
-------------
Disk Requirements:
  At least 12MB more space needed on the /boot filesystem.

古いカーネルを削除

# package-cleanup --oldkernels
# yum update