diff -u b/core/modules/serialization/tests/src/Unit/Normalizer/NormalizerBaseTest.php b/core/modules/serialization/tests/src/Unit/Normalizer/NormalizerBaseTest.php
--- b/core/modules/serialization/tests/src/Unit/Normalizer/NormalizerBaseTest.php
+++ b/core/modules/serialization/tests/src/Unit/Normalizer/NormalizerBaseTest.php
@@ -75,7 +75,7 @@
    *
    * @dataProvider providerTestSupportsDenormalization
    */
-  public function testSupportsDenormalization($expected_return, $data, $supported_interface_or_class = NULL, array $supported_types = []) {
+  public function testSupportsDenormalization($expected_return, $data, $supported_interface_or_class = NULL, $supported_types = NULL) {
     $normalizer_base = $this->getMockForAbstractClass(TestNormalizerBase::class);
 
     if (!empty($supported_types)) {