diff --git a/modpypes/app.py b/modpypes/app.py
index b8a1064..b7ae5a6 100644
--- a/modpypes/app.py
+++ b/modpypes/app.py
@@ -7,6 +7,7 @@ Application
 """
 
 import sys
+import struct
 
 from bacpypes.debugging import bacpypes_debugging, ModuleLogger
 
@@ -21,17 +22,6 @@ _debug = 0
 _log = ModuleLogger(globals())
 
 
-#
-#   _ord
-#
-
-if sys.version_info[0] == 2:
-    _ord = lambda s: ord(s)
-elif sys.version_info[0] == 3:
-    _ord = lambda s: s
-else:
-    raise RuntimeError("unrecognized Python version")
-
 #
 #   ModbusException
 #
@@ -80,8 +70,8 @@ def stream_to_packet(data):
     if len(data) < 6:
         return None
 
-    # note funky _ord function, a noop in Python3
-    pktlen = (_ord(data[4]) << 8) + _ord(data[5]) + 6
+    # unpack the length
+    pktlen = struct.unpack(">H", data[4:6])[0] + 6
     if (len(data) < pktlen):
         return None