"No package 'json-c' found"

[raoulteeuwen]

Setting up a new RPi4 with latest Raspbian. After step "autogen.sh" i eventually run into

checking pkg-config is at least version 0.9.0... yes
checking for JSON_C... no
configure: error: Package requirements (json-c) were not met:

No package 'json-c' found

Consider adjusting the PKG_CONFIG_PATH environment variable if you
installed software in a non-standard prefix.

Alternatively, you may set the environment variables JSON_C_CFLAGS
and JSON_C_LIBS to avoid the need to call pkg-config.
See the pkg-config man page for more details.

Have tried to solve it, but no joy yet.