Kernel Initrd Crash: No CPIO Magic
 

I use Debian Etch with standard mkinitrd.deb package.
I had compiled the latest version of kernel 2.6.29.1

I created initrd using the following command:
mkinitrd -o initrd-2.6.29.1 2.6.29.1

The result is compressed using gzip:
gzip initrd-2.6.29.1

Then I copy the result to /boot:
cp initrd-2.6.29.1 /boot/initrd.img-2.6.29.1

The new Initrd image crash during bootup with the following message:

Unpacking initramfs...<0>Kernel panic - not syncing: no cpio magic

How to solve this problem?
Is the above method a correct way to create initrd image file?

Thank you.