diff --git a/plusone-validator/src/main/java/xyz/zhouxy/plusone/validator/ObjectPropertyValidator.java b/plusone-validator/src/main/java/xyz/zhouxy/plusone/validator/ObjectPropertyValidator.java
index ccacc8c..f8c5c8b 100644
--- a/plusone-validator/src/main/java/xyz/zhouxy/plusone/validator/ObjectPropertyValidator.java
+++ b/plusone-validator/src/main/java/xyz/zhouxy/plusone/validator/ObjectPropertyValidator.java
@@ -28,7 +28,7 @@ import java.util.function.Function;
 public class ObjectPropertyValidator<T, TProperty>
         extends BasePropertyValidator<T, TProperty, ObjectPropertyValidator<T, TProperty>> {
 
-    ObjectPropertyValidator(Function<T, TProperty> getter) {
+    ObjectPropertyValidator(Function<T, ? extends TProperty> getter) {
         super(getter);
     }