dnl C programming environment.
PKG_CHECK_MODULES([mLib], [mLib >= 2.1.0])
-PKG_CHECK_MODULES([nettle], [nettle >= 2.4])
+PKG_CHECK_MODULES([nettle], [nettle >= 2.4], [], [
+ ## That didn't work; unfortunately older Nettle packages don't have a
+ ## pkg-config dropping. Let's see whether it will work anyway.
+ nettlep=t
+ AC_CHECK_HEADER([nettle/sha.h], [], [nettlep=nil])
+ AC_CHECK_LIB([nettle], [nettle_sha256_init], [], [nettlep=nil])
+ case $nettlep in
+ nil) AC_MSG_ERROR([Failed to find Nettle library.]) ;;
+ esac
+ NETTLE_CFLAGS= NETTLE_LIBS=-lnettle])
dnl--------------------------------------------------------------------------
dnl Perl programming environment.