diff --git a/Classes/PHPExcel/Calculation.php b/Classes/PHPExcel/Calculation.php
index 2fc63e5..70f8d12 100644
--- a/Classes/PHPExcel/Calculation.php
+++ b/Classes/PHPExcel/Calculation.php
@@ -1681,14 +1681,6 @@ class PHPExcel_Calculation {
 
 
 	private function __construct() {
-		$localeFileDirectory = PHPEXCEL_ROOT.'PHPExcel/locale/';
-		foreach (glob($localeFileDirectory.'/*',GLOB_ONLYDIR) as $filename) {
-			$filename = substr($filename,strlen($localeFileDirectory)+1);
-			if ($filename != 'en') {
-				self::$_validLocaleLanguages[] = $filename;
-			}
-		}
-
 		$setPrecision = (PHP_INT_SIZE == 4) ? 12 : 16;
 		$this->_savedPrecision = ini_get('precision');
 		if ($this->_savedPrecision < $setPrecision) {
@@ -1703,6 +1695,16 @@ class PHPExcel_Calculation {
 		}
 	}
 
+	private static function _loadLocales() {
+		$localeFileDirectory = PHPEXCEL_ROOT.'PHPExcel/locale/';
+		foreach (glob($localeFileDirectory.'/*',GLOB_ONLYDIR) as $filename) {
+			$filename = substr($filename,strlen($localeFileDirectory)+1);
+			if ($filename != 'en') {
+				self::$_validLocaleLanguages[] = $filename;
+			}
+		}
+	}
+
 	/**
 	 * Get an instance of this class
 	 *
@@ -1883,6 +1885,9 @@ class PHPExcel_Calculation {
 			list($language) = explode('_',$locale);
 		}
 
+		if (count(self::$_validLocaleLanguages) == 1)
+			self::_loadLocales();
+
 		//	Test whether we have any language data for this language (any locale)
 		if (in_array($language,self::$_validLocaleLanguages)) {
 			//	initialise language/locale settings