diff --git a/core/tests/Drupal/Tests/Core/Image/ImageTest.php b/core/tests/Drupal/Tests/Core/Image/ImageTest.php
index 04b79fb..a553691 100644
--- a/core/tests/Drupal/Tests/Core/Image/ImageTest.php
+++ b/core/tests/Drupal/Tests/Core/Image/ImageTest.php
@@ -65,6 +65,10 @@ protected function setUp() {
    */
   public function testGetExtension() {
     $this->assertEquals($this->image->getExtension(), 'png');
+
+    // Test the fallback pathinfo() behavior.
+    $image = new Image(__DIR__ . '/../../../../../misc/druplicon-non-existent.png', $this->toolkit);
+    $this->assertEquals($image->getExtension(), 'png');
   }
 
   /**