diff --git a/core/modules/migrate_drupal/tests/fixtures/drupal6.php b/core/modules/migrate_drupal/tests/fixtures/drupal6.php
index 9334ac0..2ecce69 100644
--- a/core/modules/migrate_drupal/tests/fixtures/drupal6.php
+++ b/core/modules/migrate_drupal/tests/fixtures/drupal6.php
@@ -46583,6 +46583,12 @@
   'dst' => 'the-zulu-people',
   'language' => 'en',
 ))
+->values(array(
+  'pid' => '8',
+  'src' => 'admin',
+  'dst' => 'noslash',
+  'language' => '',
+))
 ->execute();
 
 $connection->schema()->createTable('users', array(
diff --git a/core/modules/path/migrations/d6_url_alias.yml b/core/modules/path/migrations/d6_url_alias.yml
index fcf2036..c5d7934 100644
--- a/core/modules/path/migrations/d6_url_alias.yml
+++ b/core/modules/path/migrations/d6_url_alias.yml
@@ -27,6 +27,7 @@ process:
       delimiter: /
     -
       plugin: extract
+      default: 'INVALID_NID'
       index:
         - 1
     -
diff --git a/core/modules/path/tests/src/Kernel/Migrate/d6/MigrateUrlAliasTest.php b/core/modules/path/tests/src/Kernel/Migrate/d6/MigrateUrlAliasTest.php
index 092d5ac..e44b13e 100644
--- a/core/modules/path/tests/src/Kernel/Migrate/d6/MigrateUrlAliasTest.php
+++ b/core/modules/path/tests/src/Kernel/Migrate/d6/MigrateUrlAliasTest.php
@@ -132,6 +132,11 @@ public function testUrlAliasWithTranslatedNodes() {
     $path = $alias_storage->load(['alias' => '/the-zulu-people']);
     $this->assertSame('/node/12', $path['source']);
     $this->assertSame('en', $path['langcode']);
+
+    // Alias for 'admin', an alias without a slash.
+    $path = $alias_storage->load(['alias' => '/noslash']);
+    $this->assertSame('/admin', $path['source']);
+    $this->assertSame('und', $path['langcode']);
   }
 
 }