linux – Bash history limited to 1000 even with HISTSIZE=-1

On my old notebook (Debian sid) I had this in my ~/.bashrc and it used to work (e.g. history was more or less unlimited and it was being saved on each command):

export PROMPT_COMMAND='printf "33)0;%s@%s:%s07" "lucio" "t470" "/home/lucio/virtualbit/progetti/workspace/vscode/teom/websi"'
export PS1='(e(1;31m)u(e(1;33m)@(e(1;36m)h (e(1;33m)w (e(1;35m)$ (e(0m)'
export HISTFILESIZE=9999999
export HISTSIZE=9999999
export HISTTIMEFORMAT="%d/%m/%y %T "
shopt -s histappend
export PROMPT_COMMAND="history -a;history -a;printf "33)0;%s@%s:%s07" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}""

I coped over the same ~/.bashrc on my new notebook (Debian sid like the old one) and verified it’s being applied:

$ echo $HISTSIZE

Then I tried with HISTSIZE=-1 in my ~/.bashrc with same results: my history is being cut at 1000 lines. Any clues?