diff --git a/tests/phpunit/tests/functions/pluginBasename.php b/tests/phpunit/tests/functions/pluginBasename.php
index c7a90e23c3..fb8a7d858d 100644
--- a/tests/phpunit/tests/functions/pluginBasename.php
+++ b/tests/phpunit/tests/functions/pluginBasename.php
@@ -16,7 +16,7 @@ class Tests_Plugin_Basename extends WP_UnitTestCase {
 
 		$old_wp_plugin_paths = $wp_plugin_paths;
 
-		$wp_plugin_paths[ WP_PLUGIN_DIR . '/a-symlinked-plugin' ] = 'C:/www/path/plugins/a-plugin';
+		$wp_plugin_paths[ wp_normalize_path( WP_PLUGIN_DIR ) . '/a-symlinked-plugin' ] = 'C:/www/path/plugins/a-plugin';
 
 		$basename = plugin_basename( 'c:\www\path\plugins\a-plugin\plugin.php' );