diff --git a/internal/builder/kraftfile.go b/internal/builder/kraftfile.go
index 82f84419..687acfcc 100644
--- a/internal/builder/kraftfile.go
+++ b/internal/builder/kraftfile.go
@@ -54,12 +54,11 @@ func KraftfileToBuildOpts(dir string, kf *kraftfile.Kraftfile) (BuildOpts, error
 	}
 
 	if kf.Rootfs != nil {
-		opts.Rootfs.Path = kf.Rootfs.Source
+		opts.Rootfs.Path = filepath.Join(dir, kf.Rootfs.Source)
 		opts.Rootfs.Format = kf.Rootfs.Format
 		opts.Rootfs.Type = kf.Rootfs.Type
 		if opts.Rootfs.Type == "" {
-			sourcePath := filepath.Join(dir, kf.Rootfs.Source)
-			typ, err := DetectSourceType(sourcePath)
+			typ, err := DetectSourceType(opts.Rootfs.Path)
 			if err != nil {
 				return BuildOpts{}, fmt.Errorf("detecting rootfs type for %q: %w", kf.Rootfs.Source, err)
 			}
diff --git a/internal/builder/kraftfile_test.go b/internal/builder/kraftfile_test.go
index c7378620..97ace861 100644
--- a/internal/builder/kraftfile_test.go
+++ b/internal/builder/kraftfile_test.go
@@ -46,7 +46,7 @@ func TestKraftfileToBuildOpts(t *testing.T) {
 	require.Equal(t, map[string]string{"label": "value"}, opts.Labels)
 	require.Equal(t, "unikraft.io/unikraft.org/base", opts.Runtime)
 	require.Equal(t, kraftfile.FsTypeErofs, opts.Rootfs.Format)
-	require.Equal(t, "Dockerfile", opts.Rootfs.Path)
+	require.Equal(t, rootfsDir+"/Dockerfile", opts.Rootfs.Path)
 	require.Equal(t, kraftfile.SourceTypeDockerfile, opts.Rootfs.Type)
 	require.Len(t, opts.Platform, 1)
 	require.Equal(t, "x86_64", opts.Platform[0].Architecture)
@@ -75,6 +75,24 @@ func TestKraftfileToBuildOptsRootfsSourceError(t *testing.T) {
 	require.Error(t, err)
 }
 
+func TestKraftfileToBuildOptsRootfsPathJoined(t *testing.T) {
+	rootfsDir := t.TempDir()
+
+	runtime := kraftfile.Runtime("unikraft.io/unikraft.org/base")
+	kf := &kraftfile.Kraftfile{
+		Runtime: &runtime,
+		Rootfs: &kraftfile.FS{
+			Format: kraftfile.FsTypeErofs,
+			Source: "Dockerfile",
+		},
+	}
+
+	opts, err := KraftfileToBuildOpts(rootfsDir, kf)
+	require.NoError(t, err)
+	require.Equal(t, rootfsDir+"/Dockerfile", opts.Rootfs.Path,
+		"rootfs path must be joined with the kraftfile directory")
+}
+
 func TestKraftfileToBuildOptsNoRootfs(t *testing.T) {
 	rootfsDir := t.TempDir()