diff --git a/contrib/pyln-proto/pyln/proto/message/message.py b/contrib/pyln-proto/pyln/proto/message/message.py
index e43d497a7..c40464c66 100644
--- a/contrib/pyln-proto/pyln/proto/message/message.py
+++ b/contrib/pyln-proto/pyln/proto/message/message.py
@@ -109,10 +109,11 @@ domain, such as within a given BOLT"""
 
 class MessageTypeField(object):
     """A field within a particular message type or subtype"""
-    def __init__(self, ownername, name, fieldtype):
+    def __init__(self, ownername, name, fieldtype, option=None):
         self.full_name = "{}.{}".format(ownername, name)
         self.name = name
         self.fieldtype = fieldtype
+        self.option = option
 
     def missing_fields(self, fields):
         """Return this field if it's not in fields"""
@@ -171,7 +172,7 @@ inherit from this too.
                              .format(parts))
         return SubtypeType(parts[0])
 
-    def _field_from_csv(self, namespace, parts, ellipsisok=False):
+    def _field_from_csv(self, namespace, parts, ellipsisok=False, option=None):
         """Takes msgdata/subtypedata after first two fields
         e.g. [...]timestamp_node_id_1,u32,
 
@@ -191,19 +192,22 @@ inherit from this too.
                                          DynamicArrayType(self,
                                                           parts[0],
                                                           basetype,
-                                                          lenfield))
+                                                          lenfield),
+                                         option)
                 lenfield.fieldtype.add_length_for(field)
             elif ellipsisok and parts[2] == '...':
                 field = MessageTypeField(self.name, parts[0],
                                          EllipsisArrayType(self,
-                                                           parts[0], basetype))
+                                                           parts[0], basetype),
+                                         option)
             else:
                 field = MessageTypeField(self.name, parts[0],
                                          SizedArrayType(self,
                                                         parts[0], basetype,
-                                                        int(parts[2])))
+                                                        int(parts[2])),
+                                         option)
         else:
-            field = MessageTypeField(self.name, parts[0], basetype)
+            field = MessageTypeField(self.name, parts[0], basetype, option)
 
         return field
 
@@ -299,9 +303,10 @@ class MessageType(SubtypeType):
                    'NODE': 0x2000,
                    'UPDATE': 0x1000}
 
-    def __init__(self, name, value):
+    def __init__(self, name, value, option=None):
         super().__init__(name)
         self.number = self.parse_value(value)
+        self.option = option
 
     def parse_value(self, value):
         result = 0
@@ -318,23 +323,30 @@ class MessageType(SubtypeType):
 
     @staticmethod
     def type_from_csv(parts):
-        """e.g msgtype,open_channel,32"""
-        if len(parts) != 2:
+        """e.g msgtype,open_channel,32,option_foo"""
+        option = None
+        if len(parts) == 3:
+            option = parts[2]
+        elif len(parts) < 2 or len(parts) > 3:
             raise ValueError("msgtype expected 3 CSV parts, not {}"
                              .format(parts))
-        return MessageType(parts[0], parts[1])
+        return MessageType(parts[0], parts[1], option)
 
     @staticmethod
     def field_from_csv(namespace, parts):
-        """e.g msgdata,open_channel,temporary_channel_id,byte,32"""
-        if len(parts) != 4:
+        """e.g msgdata,open_channel,temporary_channel_id,byte,32[,opt]"""
+        option = None
+        if len(parts) == 5:
+            option = parts[4]
+        elif len(parts) != 4:
             raise ValueError("msgdata expected 4 CSV parts, not {}"
                              .format(parts))
         messagetype = namespace.get_msgtype(parts[0])
         if not messagetype:
             raise ValueError("unknown subtype {}".format(parts[0]))
 
-        field = messagetype._field_from_csv(namespace, parts[1:])
+        field = messagetype._field_from_csv(namespace, parts[1:4],
+                                            option=option)
         messagetype.add_field(field)