diff --git a/core/modules/field/src/Plugin/migrate/source/d7/FieldInstance.php b/core/modules/field/src/Plugin/migrate/source/d7/FieldInstance.php
index 74340884d2..a6b8cf2b39 100644
--- a/core/modules/field/src/Plugin/migrate/source/d7/FieldInstance.php
+++ b/core/modules/field/src/Plugin/migrate/source/d7/FieldInstance.php
@@ -181,7 +181,7 @@ public function prepareRow(Row $row) {
     }
 
     $field_data = unserialize($row->getSourceProperty('field_data'));
-    $row->setSourceProperty('field_settings', $field_data['settings']);
+    $row->setSourceProperty('field_settings', $field_data['settings'] ?? NULL);
 
     return parent::prepareRow($row);
   }
diff --git a/core/modules/field/tests/src/Kernel/FieldFormatterTest.php b/core/modules/field/tests/src/Kernel/FieldFormatterTest.php
index f61ea3ff3a..7d22271a69 100644
--- a/core/modules/field/tests/src/Kernel/FieldFormatterTest.php
+++ b/core/modules/field/tests/src/Kernel/FieldFormatterTest.php
@@ -98,7 +98,7 @@ public function testThirdPartySettings() {
 
     $entity->{$this->fieldName}->value = $this->randomString();
     $build = $entity->{$this->fieldName}->view('default');
-    $this->assertEquals($third_party_settings, $build['#third_party_settings']);
+    $this->assertEquals($third_party_settings, $build['#third_party_settings'] ?? NULL);
   }
 
 }
diff --git a/core/modules/migrate/tests/src/Kernel/MigrateConfigRollbackTest.php b/core/modules/migrate/tests/src/Kernel/MigrateConfigRollbackTest.php
index 27aa45bcce..1c5cdd49a4 100644
--- a/core/modules/migrate/tests/src/Kernel/MigrateConfigRollbackTest.php
+++ b/core/modules/migrate/tests/src/Kernel/MigrateConfigRollbackTest.php
@@ -79,7 +79,7 @@ public function testConfigRollback() {
     $this->assertSame('Awesome slogan', $config->get('slogan'));
     // Confirm the map row is deleted.
     $map_row = $config_id_map->getRowBySource(['id' => $variable[0]['id']]);
-    $this->assertNull($map_row['destid1']);
+    $this->assertNull($map_row['destid1'] ?? NULL);
 
     // We use system configuration to demonstrate importing and rolling back
     // configuration translations.
diff --git a/core/modules/taxonomy/src/Plugin/migrate/source/d6/TermLocalizedTranslation.php b/core/modules/taxonomy/src/Plugin/migrate/source/d6/TermLocalizedTranslation.php
index 844fb858b5..d29b57be3c 100644
--- a/core/modules/taxonomy/src/Plugin/migrate/source/d6/TermLocalizedTranslation.php
+++ b/core/modules/taxonomy/src/Plugin/migrate/source/d6/TermLocalizedTranslation.php
@@ -70,7 +70,7 @@ public function prepareRow(Row $row) {
     $query->condition('lt.language', $language);
     $query->addField('lt', 'translation');
     $results = $query->execute()->fetchAssoc();
-    $row->setSourceProperty($other_property . '_translated', $results['translation']);
+    $row->setSourceProperty($other_property . '_translated', $results['translation'] ?? NULL);
 
     parent::prepareRow($row);
   }
diff --git a/core/tests/Drupal/KernelTests/Core/Entity/EntityTranslationTest.php b/core/tests/Drupal/KernelTests/Core/Entity/EntityTranslationTest.php
index aa2a999f2d..4e44c67195 100644
--- a/core/tests/Drupal/KernelTests/Core/Entity/EntityTranslationTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Entity/EntityTranslationTest.php
@@ -664,7 +664,7 @@ protected function doTestLanguageFallback($entity_type) {
     $controller = $this->entityTypeManager->getViewBuilder($entity_type);
     $build = $controller->view($entity);
     $renderer->renderRoot($build);
-    $this->assertEqual($build['label']['#markup'], $values[$current_langcode]['name'], 'By default the entity is rendered in the current language.');
+    $this->assertEqual($build['label']['#markup'] ?? NULL, $values[$current_langcode]['name'], 'By default the entity is rendered in the current language.');
 
     $langcodes = array_combine($this->langcodes, $this->langcodes);
     // We have no translation for the $langcode2 language, hence the expected
diff --git a/core/tests/Drupal/KernelTests/Core/Entity/EntityViewBuilderTest.php b/core/tests/Drupal/KernelTests/Core/Entity/EntityViewBuilderTest.php
index 4172772be7..c3932c8b3a 100644
--- a/core/tests/Drupal/KernelTests/Core/Entity/EntityViewBuilderTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Entity/EntityViewBuilderTest.php
@@ -194,7 +194,7 @@ public function testEntityViewBuilderWeight() {
     $renderer->renderRoot($view);
 
     // Check that the weight is respected.
-    $this->assertEqual($view['label']['#weight'], 20, 'The weight of a display component is respected.');
+    $this->assertEqual($view['label']['#weight'] ?? NULL, 20, 'The weight of a display component is respected.');
   }
 
   /**
diff --git a/core/tests/Drupal/KernelTests/KernelTestBase.php b/core/tests/Drupal/KernelTests/KernelTestBase.php
index 290e494aea..c354a38461 100644
--- a/core/tests/Drupal/KernelTests/KernelTestBase.php
+++ b/core/tests/Drupal/KernelTests/KernelTestBase.php
@@ -607,7 +607,7 @@ protected function tearDown() {
     $original_connection_info = Database::getConnectionInfo('simpletest_original_default');
     $original_prefix = $original_connection_info['default']['prefix']['default'] ?? NULL;
     $test_connection_info = Database::getConnectionInfo('default');
-    $test_prefix = $test_connection_info['default']['prefix']['default'];
+    $test_prefix = $test_connection_info['default']['prefix']['default'] ?? NULL;
     if ($original_prefix != $test_prefix) {
       $tables = Database::getConnection()->schema()->findTables('%');
       foreach ($tables as $table) {