config.txt “total_mem=1024” breaks Pi1 boot

I maintain several Pi’s using the same “config.txt” file and have a small issue.
The Pi1 doesn’t boot when there is option “total_mem=1024” in config.txt file present.

This happen when the option is global

total_mem=1024

and also when it the option is in [pi2] or [pi3] part only

[pi2]
total_mem=1024
[pi3]
total_mem=1024
[all]

This is not a big issue because I simply remove it with a # comment