Cannot update new kernel for CentOS 7 although the server have space enough

I try to update kernel on my CentOS 7 but the yum say there is no space enough on /boot although /boot have 343 MB as show below:

Filesystem Size Used Avail Use% Mounted on /dev/sda2 477M 105M 343M 24% /boot

Here the error that I got:

Transaction check error: installing package kernel-3.10.0-123.9.2.el7.x86_64 needs 30MB on the /boot filesystem

That's weird.