diff --git a/macro.go b/macro.go
index 706c0ab..01b80ee 100644
--- a/macro.go
+++ b/macro.go
@@ -61,6 +61,16 @@ func MacroI[T any](f func(t T) carapace.Action) Macro {
 				if err := yaml.Unmarshal([]byte(s), &t); err != nil {
 					return carapace.ActionMessage(err.Error())
 				}
+
+				if s == "" {
+					if m := reflect.ValueOf(&t).MethodByName("Default"); m.IsValid() && m.Type().NumIn() == 0 {
+						values := m.Call([]reflect.Value{}) // TODO check if needs args
+						if len(values) > 0 && values[0].Type().AssignableTo(reflect.TypeOf(t)) {
+							reflect.ValueOf(&t).Elem().Set(values[0])
+						}
+					}
+
+				}
 			}
 			return f(t)
 		},
diff --git a/macro_test.go b/macro_test.go
index a395768..e77255b 100644
--- a/macro_test.go
+++ b/macro_test.go
@@ -11,6 +11,11 @@ type Arg struct {
 	Option bool
 }
 
+func (a Arg) Default() Arg {
+	a.Option = true
+	return a
+}
+
 func TestSignature(t *testing.T) {
 	signature := MacroI(func(a Arg) carapace.Action { return carapace.ActionValues() }).Signature()
 	if expected := `{name: "", option: false}`; signature != expected {
@@ -42,3 +47,16 @@ func TestSignature(t *testing.T) {
 		t.Errorf("should be: %v", expected)
 	}
 }
+
+func TestDefault(t *testing.T) {
+	var actual Arg
+	m := MacroI(func(a Arg) carapace.Action { actual = a; return carapace.ActionValues() })
+
+	if m.f(""); !actual.Option {
+		t.Error("should be true (default)")
+	}
+
+	if m.f("{option: false}"); actual.Option {
+		t.Error("should be false")
+	}
+}