diff --git a/cmd/oras/internal/option/spec.go b/cmd/oras/internal/option/spec.go
index 76410b7e7..f9bd50f23 100644
--- a/cmd/oras/internal/option/spec.go
+++ b/cmd/oras/internal/option/spec.go
@@ -80,8 +80,9 @@ func (is *ImageSpec) String() string {
 // ApplyFlags applies flags to a command flag set.
 func (is *ImageSpec) ApplyFlags(fs *pflag.FlagSet) {
 	// default to auto
-	is.PackVersion = oras.PackManifestVersion1_1
 	defaultFlag := ImageSpecAuto
+	is.PackVersion = oras.PackManifestVersion1_1
+	is.Flag = defaultFlag
 	fs.Var(is, "image-spec", fmt.Sprintf(`[Experimental] specify manifest type for building artifact. Options: %s (default %q)`, is.Options(), defaultFlag))
 }