diff --git a/illegal/field_test.go b/illegal/field_test.go
index ed978fe..32d1f65 100644
--- a/illegal/field_test.go
+++ b/illegal/field_test.go
@@ -14,8 +14,9 @@ func TestIllegalField(t *testing.T) {
 
 	illegal.SetPrivateField(&s, "a", 10)
 	illegal.SetPrivateField(&s, "b", "foo")
+	illegal.SetPrivateField(&s, "p", internal.NewPrivateType(42))
 
-	assert.Equal(t, "10 foo", s.String())
+	assert.Equal(t, "10 foo 42", s.String())
 }
 
 func TestIllegalWrongFieldType(t *testing.T) {
diff --git a/illegal/internal/struct.go b/illegal/internal/struct.go
index c09a1b3..03469d7 100644
--- a/illegal/internal/struct.go
+++ b/illegal/internal/struct.go
@@ -4,11 +4,20 @@ package internal
 
 import "fmt"
 
+type privateType struct {
+	x int
+}
+
+func NewPrivateType(x int) any {
+	return privateType{x}
+}
+
 type Struct struct {
 	a int
 	b string
+	p privateType
 }
 
 func (s *Struct) String() string {
-	return fmt.Sprintf("%d %s", s.a, s.b)
+	return fmt.Sprintf("%d %s %d", s.a, s.b, s.p.x)
 }