+if test "x$GUILE_EFFECTIVE_VERSION" = "x2.0"; then
+ PKG_CHECK_MODULES([GUILE], [guile-2.0 >= 2.0.9])
+fi
+
+dnl Installation directories for .scm and .go files.
+guilemoduledir="${datarootdir}/guile/site/$GUILE_EFFECTIVE_VERSION"
+guileobjectdir="${libdir}/guile/$GUILE_EFFECTIVE_VERSION/site-ccache"
+AC_SUBST([guilemoduledir])
+AC_SUBST([guileobjectdir])
+
+dnl The GnuTLS bindings are necessary for substitutes over HTTPS and for 'guix
+dnl pull', among other things.
+GUILE_MODULE_AVAILABLE([have_gnutls], [(gnutls)])
+if test "x$have_gnutls" != "xyes"; then
+ AC_MSG_ERROR([The Guile bindings of GnuTLS are missing; please install them.])
+fi
+
+dnl Guile-JSON is used in various places.