diff --git a/core/modules/color/color.module b/core/modules/color/color.module
index ca0dc3a..698dbfe 100644
--- a/core/modules/color/color.module
+++ b/core/modules/color/color.module
@@ -399,7 +399,7 @@ function color_scheme_form_submit($form, FormStateInterface $form_state) {
   // Make sure enough memory is available.
   if (isset($info['base_image'])) {
     // Fetch source image dimensions.
-    $source = drupal_get_path('theme', $theme) . '/' . $info['base_image'];
+    $source = "theme://$theme/{$info['base_image']}";
     list($width, $height) = getimagesize($source);
 
     // We need at least a copy of the source and a target buffer of the same
diff --git a/core/modules/system/src/Tests/Theme/ThemeTest.php b/core/modules/system/src/Tests/Theme/ThemeTest.php
index ebd1f61..4eae7ae 100644
--- a/core/modules/system/src/Tests/Theme/ThemeTest.php
+++ b/core/modules/system/src/Tests/Theme/ThemeTest.php
@@ -260,7 +260,7 @@ function testClassLoading() {
    */
   public function testFindThemeTemplates() {
     $registry = $this->container->get('theme.registry')->get();
-    $templates = drupal_find_theme_templates($registry, '.html.twig', 'theme://test_theme');
+    $templates = drupal_find_theme_templates($registry, '.html.twig', drupal_get_path('theme', 'test_theme'));
     $this->assertEqual($templates['node__1']['template'], 'node--1', 'Template node--1.tpl.twig was found in test_theme.');
   }