diff --git a/python2x/crc16/crc16pure.py b/python2x/crc16/crc16pure.py
index 9319de4..7d936da 100644
--- a/python2x/crc16/crc16pure.py
+++ b/python2x/crc16/crc16pure.py
@@ -81,7 +81,7 @@ def _crc16(data, crc, table):
     return crc & 0xffff
 
 
-def crc16xmodem(data, crc=0):
+def crc16xmodem(data, crc=0xffff):
     """Calculate CRC-CCITT (XModem) variant of CRC16.
     `data`      - data for calculating CRC, must be a string
     `crc`       - initial value