diff --git a/core/modules/media/src/MediaSourceBase.php b/core/modules/media/src/MediaSourceBase.php
index 6be29088ad..d22d86ceeb 100644
--- a/core/modules/media/src/MediaSourceBase.php
+++ b/core/modules/media/src/MediaSourceBase.php
@@ -212,10 +212,8 @@ public function validateConfigurationForm(array &$form, FormStateInterface $form
    * {@inheritdoc}
    */
   public function submitConfigurationForm(array &$form, FormStateInterface $form_state) {
-    foreach ($form_state->getValues() as $config_key => $config_value) {
-      if (isset($this->configuration[$config_key])) {
-        $this->configuration[$config_key] = $config_value;
-      }
+    foreach (array_intersect_key($form_state->getValues(), $this->configuration) as $config_key => $config_value) {
+      $this->configuration[$config_key] = $config_value;
     }
 
     // If no source field is explicitly set, create it now.
diff --git a/core/modules/media/tests/src/Kernel/MediaSourceTest.php b/core/modules/media/tests/src/Kernel/MediaSourceTest.php
index bc6a8de299..f59524fd82 100644
--- a/core/modules/media/tests/src/Kernel/MediaSourceTest.php
+++ b/core/modules/media/tests/src/Kernel/MediaSourceTest.php
@@ -3,6 +3,7 @@
 namespace Drupal\Tests\media\Kernel;
 
 use Drupal\Core\Entity\EntityStorageException;
+use Drupal\Core\Form\FormState;
 use Drupal\field\Entity\FieldConfig;
 use Drupal\field\Entity\FieldStorageConfig;
 use Drupal\media\Entity\Media;
@@ -417,4 +418,26 @@ public function testSourceFieldCreation() {
     $this->assertEquals('test_constraints_type', $field->getTargetBundle(), 'Field is not targeting correct bundle.');
   }
 
+  /**
+   * Tests configuration form submit handler on the base media source plugin.
+   */
+  public function testSourceConfigurationSubmit() {
+    /** @var \Drupal\media\MediaSourceManager $manager */
+    $manager = $this->container->get('plugin.manager.media.source');
+    $form = [];
+    $form_state = new FormState();
+    $form_state->setValues(['test_config_value' => 'Somewhere over the rainbow.']);
+
+    /** @var \Drupal\media\MediaSourceInterface $source */
+    $source = $manager->createInstance('test', []);
+    $source->submitConfigurationForm($form, $form_state);
+
+    $expected = ['test_config_value' => 'Somewhere over the rainbow.', 'source_field' => 'field_media_test_1'];
+    $this->assertEquals($expected, $source->getConfiguration(), 'Submitted values were saved correctly.');
+
+    $form_state->setValue('not_relevant', 'Should not be saved in the plugin.');
+    $source->submitConfigurationForm($form, $form_state);
+    $this->assertEquals($expected, $source->getConfiguration(), 'Submitted values were saved correctly.');
+  }
+
 }