diff --git a/npp_control.py b/npp_control.py
index 90f26ce..d861c70 100644
--- a/npp_control.py
+++ b/npp_control.py
@@ -41,7 +41,7 @@
 sessionSetup['Parameters']['Capabilities']       = smb.SMB.CAP_EXTENDED_SECURITY | smb.SMB.CAP_USE_NT_ERRORS
 
 # allocate nonpaged pool size 0x15ff (padding 1 byte, AccountName 2 bytes, PrimaryDomain 2 bytes)
-sessionSetup['Data'] = pack('<H', 0x1604) + '\x00'*20
+sessionSetup['Data'] = pack('<H', 0x1604) + b'\x00'*20
 pkt.addCommand(sessionSetup)
 
 conn.sendSMB(pkt)