diff --git a/bib/cmd/bootc-image-builder/export_test.go b/bib/cmd/bootc-image-builder/export_test.go
index 8ada1c72..9b5d1f6e 100644
--- a/bib/cmd/bootc-image-builder/export_test.go
+++ b/bib/cmd/bootc-image-builder/export_test.go
@@ -7,6 +7,8 @@ var (
 	CheckMountpoints              = checkMountpoints
 	PartitionTables               = partitionTables
 	UpdateFilesystemSizes         = updateFilesystemSizes
+	GenPartitionTable             = genPartitionTable
+	CreateRand                    = createRand
 )
 
 func MockOsGetuid(new func() int) (restore func()) {
diff --git a/bib/cmd/bootc-image-builder/image.go b/bib/cmd/bootc-image-builder/image.go
index 6494bc07..8bbbd2d0 100644
--- a/bib/cmd/bootc-image-builder/image.go
+++ b/bib/cmd/bootc-image-builder/image.go
@@ -204,6 +204,32 @@ func setFSTypes(pt *disk.PartitionTable, rootfs string) error {
 	return nil
 }
 
+func genPartitionTable(c *ManifestConfig, customizations *blueprint.Customizations, rng *rand.Rand) (*disk.PartitionTable, error) {
+	basept, ok := partitionTables[c.Architecture.String()]
+	if !ok {
+		return nil, fmt.Errorf("pipelines: no partition tables defined for %s", c.Architecture)
+	}
+
+	partitioningMode := disk.RawPartitioningMode
+	if c.RootFSType == "btrfs" {
+		partitioningMode = disk.BtrfsPartitioningMode
+	}
+	if err := checkFilesystemCustomizations(customizations.GetFilesystems(), partitioningMode); err != nil {
+		return nil, err
+	}
+	fsCustomizations := updateFilesystemSizes(customizations.GetFilesystems(), c.RootfsMinsize)
+
+	pt, err := disk.NewPartitionTable(&basept, fsCustomizations, DEFAULT_SIZE, partitioningMode, nil, rng)
+	if err != nil {
+		return nil, err
+	}
+
+	if err := setFSTypes(pt, c.RootFSType); err != nil {
+		return nil, fmt.Errorf("error setting root filesystem type: %w", err)
+	}
+	return pt, nil
+}
+
 func manifestForDiskImage(c *ManifestConfig, rng *rand.Rand) (*manifest.Manifest, error) {
 	if c.Imgref == "" {
 		return nil, fmt.Errorf("pipeline: no base image defined")
@@ -267,28 +293,10 @@ func manifestForDiskImage(c *ManifestConfig, rng *rand.Rand) (*manifest.Manifest
 		img.KernelOptionsAppend = append(img.KernelOptionsAppend, kopts.Append)
 	}
 
-	basept, ok := partitionTables[c.Architecture.String()]
-	if !ok {
-		return nil, fmt.Errorf("pipelines: no partition tables defined for %s", c.Architecture)
-	}
-
-	partitioningMode := disk.RawPartitioningMode
-	if c.RootFSType == "btrfs" {
-		partitioningMode = disk.BtrfsPartitioningMode
-	}
-	if err := checkFilesystemCustomizations(customizations.GetFilesystems(), partitioningMode); err != nil {
-		return nil, err
-	}
-	fsCustomizations := updateFilesystemSizes(customizations.GetFilesystems(), c.RootfsMinsize)
-
-	pt, err := disk.NewPartitionTable(&basept, fsCustomizations, DEFAULT_SIZE, partitioningMode, nil, rng)
+	pt, err := genPartitionTable(c, customizations, rng)
 	if err != nil {
 		return nil, err
 	}
-
-	if err := setFSTypes(pt, c.RootFSType); err != nil {
-		return nil, fmt.Errorf("error setting root filesystem type: %w", err)
-	}
 	img.PartitionTable = pt
 
 	// For the bootc-disk image, the filename is the basename and the extension
diff --git a/bib/cmd/bootc-image-builder/image_test.go b/bib/cmd/bootc-image-builder/image_test.go
index e23d3017..2aef2fe1 100644
--- a/bib/cmd/bootc-image-builder/image_test.go
+++ b/bib/cmd/bootc-image-builder/image_test.go
@@ -7,6 +7,7 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
+	"github.com/osbuild/images/pkg/arch"
 	"github.com/osbuild/images/pkg/blueprint"
 	"github.com/osbuild/images/pkg/disk"
 	"github.com/osbuild/images/pkg/manifest"
@@ -347,3 +348,75 @@ func TestUpdateFilesystemSizes(t *testing.T) {
 	}
 
 }
+
+func findMountableSizeableFor(pt *disk.PartitionTable, needle string) (disk.Mountable, disk.Sizeable) {
+	var foundMnt disk.Mountable
+	var foundParent disk.Sizeable
+	pt.ForEachMountable(func(mnt disk.Mountable, path []disk.Entity) error {
+		if mnt.GetMountpoint() == needle {
+			foundMnt = mnt
+			for idx := len(path) - 1; idx >= 0; idx-- {
+				if sz, ok := path[idx].(disk.Sizeable); ok {
+					foundParent = sz
+					break
+				}
+			}
+		}
+		return nil
+	})
+	return foundMnt, foundParent
+}
+
+func TestGenPartitionTableSetsRootfsForAllFilesystemsXFS(t *testing.T) {
+	rng := bib.CreateRand()
+
+	cnf := &bib.ManifestConfig{
+		Architecture: arch.FromString("amd64"),
+		RootFSType:   "xfs",
+	}
+	cus := &blueprint.Customizations{
+		Filesystem: []blueprint.FilesystemCustomization{
+			{Mountpoint: "/var/data", MinSize: 2_000_000},
+			{Mountpoint: "/var/stuff", MinSize: 10_000_000},
+		},
+	}
+	pt, err := bib.GenPartitionTable(cnf, cus, rng)
+	assert.NoError(t, err)
+
+	for _, mntPoint := range []string{"/", "/boot", "/var/data"} {
+		mnt, _ := findMountableSizeableFor(pt, mntPoint)
+		assert.Equal(t, "xfs", mnt.GetFSType())
+	}
+	mnt, parent := findMountableSizeableFor(pt, "/var/data")
+	assert.True(t, parent.GetSize() >= 2_000_000)
+
+	mnt, parent = findMountableSizeableFor(pt, "/var/stuff")
+	assert.True(t, parent.GetSize() >= 10_000_000)
+
+	// ESP is always vfat
+	mnt, _ = findMountableSizeableFor(pt, "/boot/efi")
+	assert.Equal(t, "vfat", mnt.GetFSType())
+}
+
+func TestGenPartitionTableSetsRootfsForAllFilesystemsBtrfs(t *testing.T) {
+	rng := bib.CreateRand()
+
+	cnf := &bib.ManifestConfig{
+		Architecture: arch.FromString("amd64"),
+		RootFSType:   "btrfs",
+	}
+	cus := &blueprint.Customizations{}
+	pt, err := bib.GenPartitionTable(cnf, cus, rng)
+	assert.NoError(t, err)
+
+	mnt, _ := findMountableSizeableFor(pt, "/")
+	assert.Equal(t, "btrfs", mnt.GetFSType())
+
+	// btrfs has a default (ext4) /boot
+	mnt, _ = findMountableSizeableFor(pt, "/boot")
+	assert.Equal(t, "ext4", mnt.GetFSType())
+
+	// ESP is always vfat
+	mnt, _ = findMountableSizeableFor(pt, "/boot/efi")
+	assert.Equal(t, "vfat", mnt.GetFSType())
+}