only in patch2:
unchanged:
--- a/includes/phone.libphonenumber.inc
+++ b/includes/phone.libphonenumber.inc
@@ -246,7 +246,7 @@ function phone_libphonenumber_clean($number, $countrycode, $extension) {
     // Get the parsed phone objects, preserving the alpha characers.
     // Also, don't initialise the extension, otherwise it will be included in
     // the output below, which is wrong.
-    list($phoneutil, $phonenumber) = _phone_libphonenumber($number, $countrycode, '', TRUE);
+    list($phoneutil, $phonenumber) = _phone_libphonenumber($number, $countrycode, $extension, TRUE);
 
     // Get the actual countrycode used, in case we didn't have one before,
     // and libphonenumber was able to detect one from a country code.