diff --git a/Puc/v4p11/Autoloader.php b/Puc/v4p11/Autoloader.php
index 3f62972..24aa745 100644
--- a/Puc/v4p11/Autoloader.php
+++ b/Puc/v4p11/Autoloader.php
@@ -12,7 +12,7 @@ if ( !class_exists('Puc_v4p11_Autoloader', false) ):
 		public function __construct() {
 			$this->rootDir = dirname(__FILE__) . '/';
 
-			if ( defined('__NAMESPACE__') && __NAMESPACE__ ) {
+			if ( version_compare(PHP_VERSION, '5.3', '>=') && __NAMESPACE__ ) {
 				$namespaceWithSlash = __NAMESPACE__ . '\\';
 			} else {
 				$namespaceWithSlash = '';
diff --git a/Puc/v4p11/Factory.php b/Puc/v4p11/Factory.php
index c0141b9..c2aac5b 100644
--- a/Puc/v4p11/Factory.php
+++ b/Puc/v4p11/Factory.php
@@ -337,7 +337,7 @@ if ( !class_exists('Puc_v4p11_Factory', false) ):
 		 */
 		public static function addVersion($generalClass, $versionedClass, $version) {
 			if ( empty(self::$myMajorVersion) ) {
-				$className = (defined('__NAMESPACE__') && __NAMESPACE__)
+				$className = (version_compare(PHP_VERSION, '5.3', '>=') && __NAMESPACE__)
 					? substr(__CLASS__, strlen(__NAMESPACE__) + 1)
 					: __CLASS__;