diff --git a/hsldap2vcard/__init__.py b/hsldap2vcard/__init__.py
index 6701a4f..8d3318e 100644
--- a/hsldap2vcard/__init__.py
+++ b/hsldap2vcard/__init__.py
@@ -20,7 +20,7 @@ def normalize_mobile(mobile):
         pass
     else:
         raise ValueError("invalid moble: {mobile}")
-
+    return mobile
 
 class HsLdap:
     def __init__(self, uid, password):