fix #1175

lib/mnemonic.py

@@ -106,7 +106,8 @@ class Mnemonic(object):
     # Seed derivation no longer follows BIP39
     # Mnemonic phrase uses a hash based checksum, instead of a wordlist-dependent checksum
 
-    def __init__(self, lang='en'):
+    def __init__(self, lang=None):
+        lang = lang or 'en'
         print_error('language', lang)
         filename = filenames.get(lang[0:2], 'english.txt')
         path = os.path.join(os.path.dirname(__file__), 'wordlist', filename)