I am having problems with this pdftoppm

pdftoppm source.pdf target.png -png -r 50 -f 1 -l 1

I do get this warning:

Syntax Warning: Invalid Font Weight

and target.png is not generated

pdftoppm version 21.01.0

OS Release:

NAME="AlmaLinux"
VERSION="9.4 (Seafoam Ocelot)"
ID="almalinux"
ID_LIKE="rhel centos fedora"
VERSION_ID="9.4"
PLATFORM_ID="platform:el9"
PRETTY_NAME="AlmaLinux 9.4 (Seafoam Ocelot)"
ANSI_COLOR="0;34"
LOGO="fedora-logo-icon"
CPE_NAME="cpe:/o:almalinux:almalinux:9::baseos"
HOME_URL="https://almalinux.org/"
DOCUMENTATION_URL="https://wiki.almalinux.org/"
BUG_REPORT_URL="https://bugs.almalinux.org/"

ALMALINUX_MANTISBT_PROJECT="AlmaLinux-9"
ALMALINUX_MANTISBT_PROJECT_VERSION="9.4"
REDHAT_SUPPORT_PRODUCT="AlmaLinux"
REDHAT_SUPPORT_PRODUCT_VERSION="9.4"
SUPPORT_END=2032-06-01

any help please?