If you were following instructions in https://idjc.sourceforge.io/install_build.html, when installing idcj, in this step... ./configure CFLAGS="-O2" --prefix=/usr --libdir=/usr/lib64 ... you can prefix it with PKG_CONFIG_PATH like this: PKG_CONFIG_PATH=/usr/lib64/pkgconfig ./configure CFLAGS="-O2" --prefix=/usr --libdir=/usr/lib64 Hope it works :)