diff --git a/configure.ac b/configure.ac
index 75f9525..a627feb 100644
--- a/configure.ac
+++ b/configure.ac
@@ -22,6 +22,26 @@ AC_CONFIG_FILES([
 
 AC_SUBST([GUIX_BUILD_MAX_CORES], [])
 
+# When the Guix revision changes, the output changes, so we need to
+# rebuild it. By not having the revision configurable through
+# configure arguments, we make things easier because when the
+# Makefiles are updated, things should be rebuilt anyway.
+#
+# In addition we currently use a released Guix revision and backport
+# the changes we need from more recent Guix versions for several
+# reasons:
+#
+# - Guix hosts the documentation of its latest release on its website,
+#   so by using the latest Guix release, we also enable GNU Boot
+#   contributors to have access to the corresponding Guix
+#   documentation without having to build and/or host it.
+#
+# - On most distributions, users don't need to run guix pull anymore
+#   to start downloading Guix 1.4.0 packages. So that can make things
+#   a lot faster.
+
+AC_SUBST([GUIX_REVISION], [v1.4.0])
+
 # --with-guix-build-max-cores
 AC_ARG_WITH([guix-build-max-cores],
     [AS_HELP_STRING([--with-guix-build-max-cores=N],
@@ -36,6 +56,13 @@ AS_IF([test x"$FOUND_GUIX" = x""],
       [AC_MSG_ERROR(
       [guix was not found in PATH ($PATH)])])
 
+# Generate a config.sh file to enable script shell to retrieve some
+# settings by sourcing it.
+printf '#!/usr/bin/env bash\n' > config.sh
+printf '# This file is generated by configure.ac\n' >> config.sh
+printf 'GUIX_REVISION=%s\n' "$GUIX_REVISION" >> config.sh
+chmod +x config.sh
+
 AC_OUTPUT
 
 AS_ECHO(["Configuration options:"])
diff --git a/resources/packages/i945-thinkpads-install-utilities/Makefile.am b/resources/packages/i945-thinkpads-install-utilities/Makefile.am
index 050c907..a566a6e 100644
--- a/resources/packages/i945-thinkpads-install-utilities/Makefile.am
+++ b/resources/packages/i945-thinkpads-install-utilities/Makefile.am
@@ -30,13 +30,13 @@ RELEASE_DIR = $(DESTDIR)/i945-thinkpads-install
 # We enable caching by not making this configurable and so when the
 # Makefile isn't updated, the Guix revision doesn't change, so we
 # don't need to rebuild anything.
-GUIX_REVISION = v1.4.0
 
 GUIX_PACK_COMMAND = \
+	source $(TOPDIR)/config.sh && \
 	source resources/scripts/misc/guix.sh && \
 	source_guix_profile && \
 	guix time-machine \
-	--commit=$(GUIX_REVISION) -- \
+	--commit="$${GUIX_REVISION}" -- \
 	pack \
 	-L $(TOPDIR)/resources/guix/ \
 	-L $(TOPDIR)/resources/guix/gnuboot/patches/ \
@@ -67,9 +67,10 @@ $(RELEASE_DIR)/gnuboot_src.tar:  Makefile
 $(RELEASE_DIR)/packages_src.tar:  Makefile
 	install -d $(RELEASE_DIR)
 	tar cf $@ \
-		`source resources/scripts/misc/guix.sh && \
+		`source $(TOPDIR)/config.sh && \
+		source resources/scripts/misc/guix.sh && \
 		source_guix_profile && \
-		guix time-machine --commit=$(GUIX_REVISION) -- \
+		guix time-machine --commit="$${GUIX_REVISION}" -- \
 		build \
 		-c $(GUIX_BUILD_MAX_CORES) \
 		-L $(TOPDIR)/resources/guix/ \