Linux-headers failed to install on old debian distributions

[Roman513]

# apt install linux-headers-$(uname -r) 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
E: Unable to locate package linux-headers-4.9.0-6-amd64
E: Couldn't find any package by glob 'linux-headers-4.9.0-6-amd64'
E: Couldn't find any package by regex 'linux-headers-4.9.0-6-amd64'
# lsb_release -a | grep Desc
No LSB modules are available.
Description:	Debian GNU/Linux 9.4 (stretch)

You need to update kernel first before installing headers