diff --git a/internal/fusefrontend/root_node.go b/internal/fusefrontend/root_node.go
index 7d37520..7221be6 100644
--- a/internal/fusefrontend/root_node.go
+++ b/internal/fusefrontend/root_node.go
@@ -62,18 +62,28 @@ type RootNode struct {
 }
 
 func NewRootNode(args Args, c *contentenc.ContentEnc, n *nametransform.NameTransform) *RootNode {
+	var rootDev uint64
+	var st syscall.Stat_t
+	if err := syscall.Stat(args.Cipherdir, &st); err != nil {
+		tlog.Warn.Printf("Could not stat backing directory %q: %v", args.Cipherdir, err)
+	} else {
+		rootDev = uint64(st.Dev)
+	}
+
 	if len(args.Exclude) > 0 {
 		tlog.Warn.Printf("Forward mode does not support -exclude")
 	}
+
 	ivLen := nametransform.DirIVLen
 	if args.PlaintextNames {
 		ivLen = 0
 	}
+
 	rn := &RootNode{
 		args:          args,
 		nameTransform: n,
 		contentEnc:    c,
-		inoMap:        inomap.New(),
+		inoMap:        inomap.New(rootDev),
 		dirCache:      dirCache{ivLen: ivLen},
 		quirks:        syscallcompat.DetectQuirks(args.Cipherdir),
 	}
diff --git a/internal/fusefrontend_reverse/root_node.go b/internal/fusefrontend_reverse/root_node.go
index d4c1e37..e15ddb0 100644
--- a/internal/fusefrontend_reverse/root_node.go
+++ b/internal/fusefrontend_reverse/root_node.go
@@ -2,10 +2,13 @@ package fusefrontend_reverse
 
 import (
 	"log"
+	"os"
 	"path/filepath"
 	"strings"
 	"syscall"
 
+	"github.com/rfjakob/gocryptfs/v2/internal/exitcodes"
+
 	"github.com/rfjakob/gocryptfs/v2/internal/tlog"
 
 	"golang.org/x/sys/unix"
@@ -46,12 +49,14 @@ type RootNode struct {
 // ReverseFS provides an encrypted view.
 func NewRootNode(args fusefrontend.Args, c *contentenc.ContentEnc, n *nametransform.NameTransform) *RootNode {
 	var rootDev uint64
-	if args.OneFileSystem {
-		var st syscall.Stat_t
-		err := syscall.Stat(args.Cipherdir, &st)
-		if err != nil {
-			log.Panicf("Could not stat backing directory %q: %v", args.Cipherdir, err)
+	var st syscall.Stat_t
+	if err := syscall.Stat(args.Cipherdir, &st); err != nil {
+		tlog.Warn.Printf("Could not stat backing directory %q: %v", args.Cipherdir, err)
+		if args.OneFileSystem {
+			tlog.Fatal.Printf("This is a fatal error in combination with -one-file-system")
+			os.Exit(exitcodes.CipherDir)
 		}
+	} else {
 		rootDev = uint64(st.Dev)
 	}
 
@@ -59,7 +64,7 @@ func NewRootNode(args fusefrontend.Args, c *contentenc.ContentEnc, n *nametransf
 		args:          args,
 		nameTransform: n,
 		contentEnc:    c,
-		inoMap:        inomap.New(),
+		inoMap:        inomap.New(rootDev),
 		rootDev:       rootDev,
 	}
 	if len(args.Exclude) > 0 || len(args.ExcludeWildcard) > 0 || len(args.ExcludeFrom) > 0 {
diff --git a/internal/inomap/inomap.go b/internal/inomap/inomap.go
index 97f9b61..997ea9b 100644
--- a/internal/inomap/inomap.go
+++ b/internal/inomap/inomap.go
@@ -49,13 +49,22 @@ type InoMap struct {
 }
 
 // New returns a new InoMap.
-func New() *InoMap {
-	return &InoMap{
+// Inode numbers on device `rootDev` will be passed through as-is.
+// If `rootDev` is zero, the first Translate() call decides the effective
+// rootDev.
+func New(rootDev uint64) *InoMap {
+	m := &InoMap{
 		namespaceMap:  make(map[namespaceData]uint16),
 		namespaceNext: 0,
 		spillMap:      make(map[QIno]uint64),
 		spillNext:     0,
 	}
+	if rootDev > 0 {
+		// Reserve namespace 0 for rootDev
+		m.namespaceMap[namespaceData{rootDev, 0}] = 0
+		m.namespaceNext = 1
+	}
+	return m
 }
 
 var spillWarn sync.Once
diff --git a/internal/inomap/inomap_test.go b/internal/inomap/inomap_test.go
index 6fbb4ef..9ec2932 100644
--- a/internal/inomap/inomap_test.go
+++ b/internal/inomap/inomap_test.go
@@ -6,7 +6,7 @@ import (
 )
 
 func TestTranslate(t *testing.T) {
-	m := New()
+	m := New(0)
 	q := QIno{Ino: 1}
 	out := m.Translate(q)
 	if out != 1 {
@@ -25,12 +25,7 @@ func TestTranslate(t *testing.T) {
 
 func TestTranslateStress(t *testing.T) {
 	const baseDev = 12345
-	m := New()
-
-	// Make sure baseDev gets namespace id zero
-	var q QIno
-	q.Dev = baseDev
-	m.Translate(q)
+	m := New(baseDev)
 
 	var wg sync.WaitGroup
 	wg.Add(4)
@@ -100,7 +95,7 @@ func TestTranslateStress(t *testing.T) {
 }
 
 func TestSpill(t *testing.T) {
-	m := New()
+	m := New(0)
 	var q QIno
 	q.Ino = maxPassthruIno + 1
 	out1 := m.Translate(q)
@@ -119,7 +114,7 @@ func TestSpill(t *testing.T) {
 // TestUniqueness checks that unique (Dev, Flags, Ino) tuples get unique inode
 // numbers
 func TestUniqueness(t *testing.T) {
-	m := New()
+	m := New(0)
 	var q QIno
 	outMap := make(map[uint64]struct{})
 	for q.Dev = 0; q.Dev < 10; q.Dev++ {
@@ -141,7 +136,7 @@ func TestUniqueness(t *testing.T) {
 }
 
 func BenchmarkTranslateSingleDev(b *testing.B) {
-	m := New()
+	m := New(0)
 	var q QIno
 	for n := 0; n < b.N; n++ {
 		q.Ino = uint64(n % 1000)
@@ -150,7 +145,7 @@ func BenchmarkTranslateSingleDev(b *testing.B) {
 }
 
 func BenchmarkTranslateManyDevs(b *testing.B) {
-	m := New()
+	m := New(0)
 	var q QIno
 	for n := 0; n < b.N; n++ {
 		q.Dev = uint64(n % 10)