diff --git a/debian/changelog b/debian/changelog
index 9f89726a..34f86795 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -5,6 +5,11 @@ livecd-rootfs (2.466) UNRELEASED; urgency=medium
   * move snap assertion handling into the generic build script (and, in
     the process, from the subiquity overlay to the base squashfs).
   * add ubuntu-mate to the set of projects we add snap model assertions to.
+  * Factor out grub-related diversions and use them consistently, so we
+    don't end up with wrong os-probe output in our grub.cfg.
+  * Fix the force-partuuid handling to create the file under
+    /etc/default/grub.d/ with a .cfg extension as grub expects; it's unclear
+    how this ever worked without.
 
  -- Steve Langasek <steve.langasek@ubuntu.com>  Wed, 04 Oct 2017 22:57:11 -0700
 
diff --git a/live-build/functions b/live-build/functions
index 7fe52f30..4b316eb5 100644
--- a/live-build/functions
+++ b/live-build/functions
@@ -277,9 +277,38 @@ replace_grub_root_with_label() {
 
     # If boot by partuuid has been requested, don't override.
     if [ -f $CHROOT_ROOT/etc/default/grub.d/40-partuuid ] && \
-           grep -q ^GRUB_FORCE_PARTUUID= $CHROOT_ROOT/etc/default/grub.d/40-partuuid; then
+           grep -q ^GRUB_FORCE_PARTUUID= $CHROOT_ROOT/etc/default/grub.d/40-partuuid.cfg; then
         return 0
     fi
     sed -i -e "s,root=[^ ]\+,root=LABEL=${fs_label}," \
         "$CHROOT_ROOT/boot/grub/grub.cfg"
 }
+
+
+# When running update-grub in a chroot on a build host, we don't want it to
+# probe for disks or probe for other installed OSes.  Extract common
+# diversion wrappers, so this isn't reinvented differently for each image.
+divert_grub() {
+	CHROOT_ROOT="$1"
+
+	chroot "$CHROOT_ROOT" dpkg-divert --local \
+		--rename /usr/sbin/grub-probe
+	chroot "$CHROOT_ROOT" touch /usr/sbin/grub-probe
+	chroot "$CHROOT_ROOT" chmod +x /usr/sbin/grub-probe
+
+	chroot "$CHROOT_ROOT" dpkg-divert --local \
+		--divert /etc/grub.d/30_os-prober.dpkg-divert \
+		--rename /etc/grub.d/30_os-prober
+}
+
+undivert_grub() {
+	CHROOT_ROOT="$1"
+
+	chroot "$CHROOT_ROOT" rm /usr/sbin/grub-probe
+	chroot "$CHROOT_ROOT" dpkg-divert --remove --local \
+		--rename /usr/sbin/grub-probe
+
+	chroot "$CHROOT_ROOT" dpkg-divert --remove --local \
+		--divert /etc/grub.d/30_os-prober.dpkg-divert \
+		--rename /etc/grub.d/30_os-prober
+}
diff --git a/live-build/ubuntu-cpc/hooks/032-disk-image.binary b/live-build/ubuntu-cpc/hooks/032-disk-image.binary
index bb8bfc11..e369dfc9 100755
--- a/live-build/ubuntu-cpc/hooks/032-disk-image.binary
+++ b/live-build/ubuntu-cpc/hooks/032-disk-image.binary
@@ -124,8 +124,10 @@ if [ "${should_install_grub}" -eq 1 ]; then
 	if [ "${SUBPROJECT:-}" = minimized ] && [ -n "$partuuid" ]; then
 		echo "partuuid found for root device; forcing it in Grub"
 		mkdir -p mountpoint/etc/default/grub.d
-		echo "GRUB_FORCE_PARTUUID=$partuuid" >> mountpoint/etc/default/grub.d/40-force-partuuid
+		echo "GRUB_FORCE_PARTUUID=$partuuid" >> mountpoint/etc/default/grub.d/40-force-partuuid.cfg
+		divert_grub mountpoint
 		chroot mountpoint update-grub
+		undivert_grub mountpoint
 	fi
 fi
 
diff --git a/live-build/ubuntu-cpc/hooks/033-disk-image-uefi.binary b/live-build/ubuntu-cpc/hooks/033-disk-image-uefi.binary
index 932484ea..8e8b0070 100755
--- a/live-build/ubuntu-cpc/hooks/033-disk-image-uefi.binary
+++ b/live-build/ubuntu-cpc/hooks/033-disk-image-uefi.binary
@@ -67,7 +67,7 @@ install_grub() {
         # and 033-disk-image-uefi.binary.  We want to fix this to not
         # have initramfs-tools installed at all on these images.
         echo "partuuid found for root device; omitting initrd"
-        echo "GRUB_FORCE_PARTUUID=$partuuid" >> mountpoint/etc/default/grub.d/40-force-partuuid
+        echo "GRUB_FORCE_PARTUUID=$partuuid" >> mountpoint/etc/default/grub.d/40-force-partuuid.cfg
     fi
 
     chroot mountpoint apt-get -y update
@@ -110,10 +110,10 @@ install_grub() {
         chroot mountpoint grub-install --target=i386-pc "${loop_device}"
     fi
 
-    chroot mountpoint dpkg-divert --local --rename /etc/grub.d/30_os-prober
+    divert_grub mountpoint
     chroot mountpoint update-grub
     replace_grub_root_with_label mountpoint
-    chroot mountpoint dpkg-divert --remove --local --rename /etc/grub.d/30_os-prober
+    undivert_grub mountpoint
 
     chroot mountpoint apt-get -y clean
 
diff --git a/live-build/ubuntu-cpc/hooks/034-disk-image-ppc64el.binary b/live-build/ubuntu-cpc/hooks/034-disk-image-ppc64el.binary
index 62a02094..649843e4 100755
--- a/live-build/ubuntu-cpc/hooks/034-disk-image-ppc64el.binary
+++ b/live-build/ubuntu-cpc/hooks/034-disk-image-ppc64el.binary
@@ -52,10 +52,10 @@ EOF
         --boot-directory=/boot \
         --target=powerpc-ieee1275
 
-    chroot mountpoint dpkg-divert --local --rename /etc/grub.d/30_os-prober
+    divert_grub mountpoint
     chroot mountpoint update-grub
     replace_grub_root_with_label mountpoint
-    chroot mountpoint dpkg-divert --remove --local --rename /etc/grub.d/30_os-prober
+    undivert_grub mountpoint
 
     umount_partition mountpoint
     rmdir mountpoint