diff --git a/py_gen/templates/oxm.py b/py_gen/templates/oxm.py
index 66886e0..5d5df7a 100644
--- a/py_gen/templates/oxm.py
+++ b/py_gen/templates/oxm.py
@@ -37,6 +37,16 @@
 import loxi.generic_util
 import loxi
 
+def unpack_list(reader):
+    def deserializer(reader):
+        type_len, = reader.peek('!L')
+        if type_len in parsers:
+            return parsers[type_len](reader)
+        else:
+            raise loxi.ProtocolError("unknown OXM cls=%#x type=%#x masked=%d len=%d (%#x)" % \
+                ((type_len >> 16) & 0xffff, (type_len >> 9) & 0x7f, (type_len >> 8) & 1, type_len & 0xff, type_len))
+    return loxi.generic_util.unpack_list(reader, deserializer)
+
 class OXM(object):
     type_len = None # override in subclass
     pass