diff --git a/bitcoinlib/mnemonic.py b/bitcoinlib/mnemonic.py
index 52612dad..54adbbf1 100644
--- a/bitcoinlib/mnemonic.py
+++ b/bitcoinlib/mnemonic.py
@@ -82,8 +82,8 @@ def to_seed(self, words, password='', validate=True):
         # Check if passphrase is valid
         if validate:
             self.to_entropy(words)
-        mnemonic = to_bytes(words)
-        password = to_bytes(password)
+        mnemonic = bytes(words, 'utf8')
+        password = bytes(password, 'utf8')
         return hashlib.pbkdf2_hmac(hash_name='sha512', password=mnemonic, salt=b'mnemonic' + password,
                                    iterations=2048)