diff --git a/composer/Plugin/Scaffold/ManageGitIgnore.php b/composer/Plugin/Scaffold/ManageGitIgnore.php
index dcb03fafcb8..524cb2ff605 100644
--- a/composer/Plugin/Scaffold/ManageGitIgnore.php
+++ b/composer/Plugin/Scaffold/ManageGitIgnore.php
@@ -61,7 +61,7 @@ class ManageGitIgnore {
         if (!$is_tracked && $scaffoldResult->isManaged()) {
           $dir = realpath(dirname($path));
           $name = basename($path);
-          $add_to_git_ignore[$dir][] = $name;
+          $add_to_git_ignore[$dir][] = '/' . $name;
         }
       }
     }
diff --git a/core/tests/Drupal/Tests/Composer/Plugin/Scaffold/Functional/ManageGitIgnoreTest.php b/core/tests/Drupal/Tests/Composer/Plugin/Scaffold/Functional/ManageGitIgnoreTest.php
index c73faf74bdf..ea965164b11 100644
--- a/core/tests/Drupal/Tests/Composer/Plugin/Scaffold/Functional/ManageGitIgnoreTest.php
+++ b/core/tests/Drupal/Tests/Composer/Plugin/Scaffold/Functional/ManageGitIgnoreTest.php
@@ -112,18 +112,18 @@ class ManageGitIgnoreTest extends TestCase {
     $this->assertFileExists($sut . '/docroot/autoload.php');
     $this->assertFileExists($sut . '/docroot/index.php');
     $expected = <<<EOT
-build
-.csslintrc
-.editorconfig
-.eslintignore
-.eslintrc.json
-.gitattributes
-.ht.router.php
-autoload.php
-index.php
-robots.txt
-update.php
-web.config
+/build
+/.csslintrc
+/.editorconfig
+/.eslintignore
+/.eslintrc.json
+/.gitattributes
+/.ht.router.php
+/autoload.php
+/index.php
+/robots.txt
+/update.php
+/web.config
 EOT;
     // At this point we should have a .gitignore file, because although we did
     // not explicitly ask for .gitignore tracking, the vendor directory is not
diff --git a/core/tests/Drupal/Tests/Composer/Plugin/Scaffold/fixtures/drupal-composer-drupal-project/docroot/.gitignore b/core/tests/Drupal/Tests/Composer/Plugin/Scaffold/fixtures/drupal-composer-drupal-project/docroot/.gitignore
index c795b054e5a..796b96d1c40 100644
--- a/core/tests/Drupal/Tests/Composer/Plugin/Scaffold/fixtures/drupal-composer-drupal-project/docroot/.gitignore
+++ b/core/tests/Drupal/Tests/Composer/Plugin/Scaffold/fixtures/drupal-composer-drupal-project/docroot/.gitignore
@@ -1 +1 @@
-build
\ No newline at end of file
+/build