diff --git a/core/lib/Drupal/Core/Validation/ConstraintManager.php b/core/lib/Drupal/Core/Validation/ConstraintManager.php
index 5dc07e61824b..228c8b397e09 100644
--- a/core/lib/Drupal/Core/Validation/ConstraintManager.php
+++ b/core/lib/Drupal/Core/Validation/ConstraintManager.php
@@ -12,6 +12,7 @@ use Drupal\Core\Validation\Plugin\Validation\Constraint\EmailConstraint;
 use Symfony\Component\Validator\Constraints\Blank;
 use Symfony\Component\Validator\Constraints\Callback;
 use Symfony\Component\Validator\Constraints\Choice;
+use Symfony\Component\Validator\Constraints\Image;
 use Symfony\Component\Validator\Constraints\NotBlank;
 
 /**
@@ -116,6 +117,11 @@ class ConstraintManager extends DefaultPluginManager {
       'class' => Choice::class,
       'type' => FALSE,
     ]);
+    $this->getDiscovery()->setDefinition('Image', [
+      'label' => new TranslatableMarkup('Image'),
+      'class' => Image::class,
+      'type' => ['string'],
+    ]);
   }
 
   /**
diff --git a/core/modules/forum/tests/fixtures/drupal7.php b/core/modules/forum/tests/fixtures/drupal7.php
index 95f92005c0b1..015d9c406876 100644
--- a/core/modules/forum/tests/fixtures/drupal7.php
+++ b/core/modules/forum/tests/fixtures/drupal7.php
@@ -30040,7 +30040,7 @@ $connection->insert('variable')
 ))
 ->values(array(
   'name' => 'image_style_preview_image',
-  'value' => 's:33:"core/modules/image/testsample.png";',
+  'value' => 's:23:"core/misc/druplicon.png";',
 ))
 ->values(array(
   'name' => 'image_toolkit',
diff --git a/core/modules/image/config/schema/image.schema.yml b/core/modules/image/config/schema/image.schema.yml
index bd438deb8229..428ba96648c4 100644
--- a/core/modules/image/config/schema/image.schema.yml
+++ b/core/modules/image/config/schema/image.schema.yml
@@ -87,10 +87,18 @@ image.effect.image_scale_and_crop:
 
 image.settings:
   type: config_object
+  constraints:
+    FullyValidatable: ~
   mapping:
     preview_image:
       type: string
       label: 'Preview image'
+      constraints:
+        NotBlank: []
+        # We need to use Symfony's Image constraint because it will accept a file
+        # path as a string, whereas the File module's FileIsImage constraint expects
+        # a full file entity.
+        Image: []
     allow_insecure_derivatives:
       type: boolean
       label: 'Allow insecure image derivatives'
diff --git a/core/modules/image/tests/src/Kernel/Migrate/d7/MigrateImageSettingsTest.php b/core/modules/image/tests/src/Kernel/Migrate/d7/MigrateImageSettingsTest.php
index da458ed2d684..ae7eb12c4e0d 100644
--- a/core/modules/image/tests/src/Kernel/Migrate/d7/MigrateImageSettingsTest.php
+++ b/core/modules/image/tests/src/Kernel/Migrate/d7/MigrateImageSettingsTest.php
@@ -29,7 +29,7 @@ class MigrateImageSettingsTest extends MigrateDrupal7TestBase {
     // These settings are not recommended...
     $this->assertTrue($config->get('allow_insecure_derivatives'));
     $this->assertTrue($config->get('suppress_itok_output'));
-    $this->assertSame("core/modules/image/testsample.png", $config->get('preview_image'));
+    $this->assertSame("core/misc/druplicon.png", $config->get('preview_image'));
   }
 
 }
diff --git a/core/modules/image/tests/src/Kernel/SettingsConfigValidationTest.php b/core/modules/image/tests/src/Kernel/SettingsConfigValidationTest.php
new file mode 100644
index 000000000000..7c78e68f247b
--- /dev/null
+++ b/core/modules/image/tests/src/Kernel/SettingsConfigValidationTest.php
@@ -0,0 +1,34 @@
+<?php
+
+namespace Drupal\Tests\image\Kernel;
+
+use Drupal\Core\Config\Schema\SchemaIncompleteException;
+use Drupal\KernelTests\KernelTestBase;
+
+/**
+ * @group image
+ */
+class SettingsConfigValidationTest extends KernelTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['image'];
+
+  /**
+   * Tests that the preview_image setting must be an existing image file.
+   */
+  public function testPreviewImagePathIsValidated(): void {
+    $this->installConfig('image');
+
+    $file = sys_get_temp_dir() . '/fake_image.png';
+    file_put_contents($file, 'Not an image!');
+
+    $this->expectException(SchemaIncompleteException::class);
+    $this->expectExceptionMessage('[preview_image] This file is not a valid image.');
+    $this->config('image.settings')
+      ->set('preview_image', $file)
+      ->save();
+  }
+
+}
diff --git a/core/modules/migrate_drupal/tests/fixtures/drupal7.php b/core/modules/migrate_drupal/tests/fixtures/drupal7.php
index 6e85c3661908..b5d57779ab80 100644
--- a/core/modules/migrate_drupal/tests/fixtures/drupal7.php
+++ b/core/modules/migrate_drupal/tests/fixtures/drupal7.php
@@ -65678,7 +65678,7 @@ $connection->insert('variable')
 ))
 ->values(array(
   'name' => 'image_style_preview_image',
-  'value' => 's:33:"core/modules/image/testsample.png";',
+  'value' => 's:23:"core/misc/druplicon.png";',
 ))
 ->values(array(
   'name' => 'image_toolkit',
diff --git a/core/modules/statistics/tests/fixtures/drupal7.php b/core/modules/statistics/tests/fixtures/drupal7.php
index a4c3130aafac..db3c26ccf688 100644
--- a/core/modules/statistics/tests/fixtures/drupal7.php
+++ b/core/modules/statistics/tests/fixtures/drupal7.php
@@ -32755,7 +32755,7 @@ $connection->insert('variable')
 ))
 ->values(array(
   'name' => 'image_style_preview_image',
-  'value' => 's:33:"core/modules/image/testsample.png";',
+  'value' => 's:23:"core/misc/druplicon.png";',
 ))
 ->values(array(
   'name' => 'image_toolkit',
diff --git a/core/modules/tracker/tests/fixtures/drupal7.php b/core/modules/tracker/tests/fixtures/drupal7.php
index 6cf600dc4aca..ea7e7dde333c 100644
--- a/core/modules/tracker/tests/fixtures/drupal7.php
+++ b/core/modules/tracker/tests/fixtures/drupal7.php
@@ -28210,7 +28210,7 @@ $connection->insert('variable')
 ))
 ->values(array(
   'name' => 'image_style_preview_image',
-  'value' => 's:33:"core/modules/image/testsample.png";',
+  'value' => 's:23:"core/misc/druplicon.png";',
 ))
 ->values(array(
   'name' => 'image_toolkit',