diff --git a/core/modules/config/src/Tests/ConfigInstallProfileOverrideTest.php b/core/modules/config/src/Tests/ConfigInstallProfileOverrideTest.php
index f3aba3b..36a0d1a 100644
--- a/core/modules/config/src/Tests/ConfigInstallProfileOverrideTest.php
+++ b/core/modules/config/src/Tests/ConfigInstallProfileOverrideTest.php
@@ -34,6 +34,9 @@ class ConfigInstallProfileOverrideTest extends WebTestBase {
    * Tests install profile config changes.
    */
   function testInstallProfileConfigOverwrite() {
+    // Ensure that an install profile can provide an site uuid.
+    $this->assertIdentical('842049cb-67f6-469a-8000-fa4a307ea577', $this->config('system.site')->get('uuid'), 'Install profiles can override system.site::uuid.');
+
     $config_name = 'system.cron';
     // The expected configuration from the system module.
     $expected_original_data = array(
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index 44212b1..817e243 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -843,7 +843,9 @@ function system_install() {
 
   // Populate the site UUID and default name (if not set).
   $site = \Drupal::configFactory()->getEditable('system.site');
-  $site->set('uuid', \Drupal::service('uuid')->generate());
+  if (!$site->get('uuid')) {
+    $site->set('uuid', \Drupal::service('uuid')->generate());
+  }
   if (!$site->get('name')) {
     $site->set('name', 'Drupal');
   }
diff --git a/core/profiles/testing_config_overrides/config/install/system.site.yml b/core/profiles/testing_config_overrides/config/install/system.site.yml
new file mode 100644
index 0000000..db5fb2f
--- /dev/null
+++ b/core/profiles/testing_config_overrides/config/install/system.site.yml
@@ -0,0 +1,12 @@
+uuid: 842049cb-67f6-469a-8000-fa4a307ea577
+name: 'Test profile for config overrides'
+mail: admin@example.com
+slogan: ''
+page:
+  403: ''
+  404: ''
+  front: /node
+admin_compact_mode: false
+weight_select_max: 100
+langcode: en
+default_langcode: en