diff --git a/core/modules/image/src/Controller/ImageStyleDownloadController.php b/core/modules/image/src/Controller/ImageStyleDownloadController.php
index f66c269656..fb10f6767b 100644
--- a/core/modules/image/src/Controller/ImageStyleDownloadController.php
+++ b/core/modules/image/src/Controller/ImageStyleDownloadController.php
@@ -123,22 +123,48 @@ public static function create(ContainerInterface $container) {
    *   Thrown when the file is still being generated.
    */
   public function deliver(Request $request, $scheme, ImageStyleInterface $image_style) {
-    $target = $request->query->get('file');
-    $image_uri = $scheme . '://' . $target;
-
     // Check that the style is defined, return a 404 (Page Not Found) if
     // missing.
     if (empty($image_style)) {
       throw new NotFoundHttpException();
     }
 
+    // Check that the URI scheme is valid, return a 404 (Page Not Found) if
+    // invalid.
+    if (!$this->streamWrapperManager->isValidScheme($scheme)) {
+      throw new NotFoundHttpException();
+    }
+
+    // Check that the source image file exists. If the image style converts
+    // the image format, the new format extension has been added to the original
+    // filename, resulting in filenames like image.png.jpeg. So to find the real
+    // source image, we remove the extension and check if that image exists.
+    $target = $request->query->get('file');
+    $request_image_uri = $scheme . '://' . $target;
+    if (file_exists($request_image_uri)) {
+      $image_uri = $request_image_uri;
+    }
+    else {
+      $path_info = pathinfo(StreamWrapperManager::getTarget($request_image_uri));
+      $dir_name = $path_info['dirname'] !== '.' ? $path_info['dirname'] . DIRECTORY_SEPARATOR : '';
+      $original_image_uri = sprintf('%s://%s%s', $scheme, $dir_name, $path_info['filename']);
+      if (file_exists($original_image_uri)) {
+        $image_uri = $original_image_uri;
+      }
+    }
+    // Don't try to generate file if source is missing.
+    if (!isset($image_uri)) {
+      $this->logger->notice('Source image at %source_image_path not found while trying to generate derivative image.', ['%source_image_path' => $request_image_uri]);
+      return new Response($this->t('Error generating image, missing source file.'), 404);
+    }
+
     // Create an image process pipeline.
     $pipeline = $this->imageProcessor->createInstance('derivative');
     $pipeline
       ->setImageStyle($image_style)
       ->setSourceImageUri($image_uri);
 
-    // Check that the scheme is valid, and the image derivative token is valid.
+    // Check that the the image derivative token is valid.
     // Sites which require image derivatives to be generated without a token
     // can set the 'image.settings:allow_insecure_derivatives' configuration to
     // TRUE to bypass the latter check, but this will increase the site's
@@ -148,7 +174,7 @@ public function deliver(Request $request, $scheme, ImageStyleInterface $image_st
     // The $target variable for a derivative of a style has
     // styles/<style_name>/... as structure, so we check if the $target variable
     // starts with styles/.
-    $valid = $this->streamWrapperManager->isValidScheme($scheme);
+    $valid = TRUE;
     if (!$this->config('image.settings')->get('allow_insecure_derivatives') || strpos(ltrim($target, '\/'), 'styles/') === 0) {
       $valid &= hash_equals($pipeline->getDerivativeImageUrlSecurityToken(), $request->query->get(IMAGE_DERIVATIVE_TOKEN, ''));
     }
@@ -172,24 +198,6 @@ public function deliver(Request $request, $scheme, ImageStyleInterface $image_st
       }
     }
 
-    // Don't try to generate file if source is missing.
-    if (!file_exists($image_uri)) {
-      // If the image style converted the extension, it has been added to the
-      // original file, resulting in filenames like image.png.jpeg. So to find
-      // the actual source image, we remove the extension and check if that
-      // image exists.
-      $path_info = pathinfo(StreamWrapperManager::getTarget($image_uri));
-      $converted_image_uri = sprintf('%s://%s%s%s', $this->streamWrapperManager->getScheme($derivative_uri), $path_info['dirname'], DIRECTORY_SEPARATOR, $path_info['filename']);
-      if (!file_exists($converted_image_uri)) {
-        $this->logger->notice('Source image at %source_image_path not found while trying to generate derivative image at %derivative_path.', ['%source_image_path' => $image_uri, '%derivative_path' => $derivative_uri]);
-        return new Response($this->t('Error generating image, missing source file.'), 404);
-      }
-      else {
-        // The converted file does exist, use it as the source.
-        $image_uri = $converted_image_uri;
-      }
-    }
-
     // Don't start generating the image if the derivative already exists or if
     // generation is in progress in another thread.
     if (!file_exists($derivative_uri)) {
diff --git a/core/modules/image/tests/src/Functional/ImageDimensionsTest.php b/core/modules/image/tests/src/Functional/ImageDimensionsTest.php
index 1260d6ba97..396136b186 100644
--- a/core/modules/image/tests/src/Functional/ImageDimensionsTest.php
+++ b/core/modules/image/tests/src/Functional/ImageDimensionsTest.php
@@ -344,7 +344,7 @@ public function testImageDimensions() {
 
     $style->addImageEffect($effect);
     $style->save();
-    $this->assertSame('<img src="' . $url . '" width="120" height="60" alt="" class="image-style-test" />', $this->getImageTag($variables));
+    $this->assertSame('<img src="' . $url . '" width="120" height="60" alt="" loading="lazy" class="image-style-test" />', $this->getImageTag($variables));
     $this->assertFileNotExists($generated_uri, 'Generated file does not exist.');
     $this->drupalGet($this->getAbsoluteUrl($url));
     $this->assertSession()->statusCodeEquals(200);
@@ -365,7 +365,7 @@ public function testImageDimensions() {
 
     $style->addImageEffect($effect);
     $style->save();
-    $this->assertSame('<img src="' . $url . '" width="60" height="120" alt="" class="image-style-test" />', $this->getImageTag($variables));
+    $this->assertSame('<img src="' . $url . '" width="60" height="120" alt="" loading="lazy" class="image-style-test" />', $this->getImageTag($variables));
     $this->assertFileNotExists($generated_uri, 'Generated file does not exist.');
     $this->drupalGet($this->getAbsoluteUrl($url));
     $this->assertSession()->statusCodeEquals(200);
@@ -387,7 +387,7 @@ public function testImageDimensions() {
 
     $style->addImageEffect($effect);
     $style->save();
-    $this->assertSame('<img src="' . $url . '" width="45" height="90" alt="" class="image-style-test" />', $this->getImageTag($variables));
+    $this->assertSame('<img src="' . $url . '" width="45" height="90" alt="" loading="lazy" class="image-style-test" />', $this->getImageTag($variables));
     $this->assertFileNotExists($generated_uri, 'Generated file does not exist.');
     $this->drupalGet($this->getAbsoluteUrl($url));
     $this->assertSession()->statusCodeEquals(200);
@@ -409,7 +409,7 @@ public function testImageDimensions() {
 
     $style->addImageEffect($effect);
     $style->save();
-    $this->assertSame('<img src="' . $url . '" width="45" height="90" alt="" class="image-style-test" />', $this->getImageTag($variables));
+    $this->assertSame('<img src="' . $url . '" width="45" height="90" alt="" loading="lazy" class="image-style-test" />', $this->getImageTag($variables));
     $this->assertFileNotExists($generated_uri, 'Generated file does not exist.');
     $this->drupalGet($this->getAbsoluteUrl($url));
     $this->assertSession()->statusCodeEquals(200);
@@ -427,7 +427,7 @@ public function testImageDimensions() {
 
     $style->addImageEffect($effect);
     $style->save();
-    $this->assertSame('<img src="' . $url . '" width="45" height="90" alt="" class="image-style-test" />', $this->getImageTag($variables));
+    $this->assertSame('<img src="' . $url . '" width="45" height="90" alt="" loading="lazy" class="image-style-test" />', $this->getImageTag($variables));
     $this->assertFileNotExists($generated_uri, 'Generated file does not exist.');
     $this->drupalGet($this->getAbsoluteUrl($url));
     $this->assertSession()->statusCodeEquals(200);
@@ -467,7 +467,7 @@ public function testImageDimensions() {
 
     $style->addImageEffect($effect);
     $style->save();
-    $this->assertEqual('<img src="' . $url . '" width="30" height="30" alt="" class="image-style-test" />', $this->getImageTag($variables));
+    $this->assertEqual('<img src="' . $url . '" width="30" height="30" alt="" loading="lazy" class="image-style-test" />', $this->getImageTag($variables));
     $this->assertFileNotExists($generated_uri, 'Generated file does not exist.');
     $this->drupalGet($this->getAbsoluteUrl($url));
     $this->assertSession()->statusCodeEquals(200);
@@ -538,7 +538,7 @@ public function testImageDimensions() {
     $generated_uri = 'public://styles/test_uri/public/' . $file_system->basename($original_uri);
     $url = file_url_transform_relative($pipeline->getDerivativeImageUrl()->toString());
 
-    $this->assertSame('<img src="' . $url . '" width="100" height="100" alt="" class="image-style-test-uri" />', $this->getImageTag($variables));
+    $this->assertSame('<img src="' . $url . '" width="100" height="100" alt="" loading="lazy" class="image-style-test-uri" />', $this->getImageTag($variables));
     $this->assertFileNotExists($generated_uri, 'Generated file does not exist.');
     $this->drupalGet($this->getAbsoluteUrl($url));
     $this->assertSession()->statusCodeEquals(200);
@@ -555,7 +555,7 @@ public function testImageDimensions() {
     $generated_uri = 'public://styles/test_uri/public/' . $file_system->basename($original_uri);
     $url = file_url_transform_relative($pipeline->getDerivativeImageUrl()->toString());
     $variables['#uri'] = $original_uri;
-    $this->assertSame('<img src="' . $url . '" width="50" height="50" alt="" class="image-style-test-uri" />', $this->getImageTag($variables));
+    $this->assertSame('<img src="' . $url . '" width="50" height="50" alt="" loading="lazy" class="image-style-test-uri" />', $this->getImageTag($variables));
     $this->assertFileNotExists($generated_uri, 'Generated file does not exist.');
     $this->drupalGet($this->getAbsoluteUrl($url));
     $this->assertSession()->statusCodeEquals(200);
diff --git a/core/modules/image/tests/src/Functional/ImageEffect/ConvertTest.php b/core/modules/image/tests/src/Functional/ImageEffect/ConvertTest.php
index 5b9d8bc4c1..29865dde20 100644
--- a/core/modules/image/tests/src/Functional/ImageEffect/ConvertTest.php
+++ b/core/modules/image/tests/src/Functional/ImageEffect/ConvertTest.php
@@ -48,11 +48,12 @@ public function testConvertFileInRoot() {
 
     // Execute the image style on the test image via a GET request.
     $pipeline = \Drupal::service('image.processor')->createInstance('derivative')
-      ->setImageStyle(ImageStyle::load('image_effect_test'))
+      ->setImageStyle($image_style)
       ->setSourceImageUri($test_uri);
     $derivative_uri = 'public://styles/image_effect_test/public/image-test-do.png.jpeg';
     $this->assertFileNotExists($derivative_uri);
-    $this->drupalGet($pipeline->getDerivativeImageUrl());
+    $url = file_url_transform_relative($pipeline->getDerivativeImageUrl()->toString());
+    $this->drupalGet($this->getAbsoluteUrl($url));
     $this->assertSession()->statusCodeEquals(200);
     $this->assertFileExists($derivative_uri);
   }