diff --git a/openflow_input/standard-1.0 b/openflow_input/standard-1.0
index d78d5bd..5483ff4 100644
--- a/openflow_input/standard-1.0
+++ b/openflow_input/standard-1.0
@@ -335,7 +335,7 @@
     uint8_t type == 4;
     uint16_t length;
     uint32_t xid;
-    uint32_t experimenter;
+    uint32_t experimenter == ?;
     uint32_t subtype;
     of_octets_t data;
 };
@@ -525,7 +525,7 @@
 struct of_action_experimenter : of_action {
     uint16_t type == 65535;
     uint16_t len;
-    uint32_t experimenter;
+    uint32_t experimenter == ?;
     of_octets_t data;
 };
 
@@ -919,7 +919,7 @@
     uint32_t xid;
     uint16_t stats_type == 0xffff;
     uint16_t flags;
-    uint32_t experimenter;
+    uint32_t experimenter == ?;
     of_octets_t data;
 };
 
@@ -930,7 +930,7 @@
     uint32_t xid;
     uint16_t stats_type == 0xffff;
     uint16_t flags;
-    uint32_t experimenter;
+    uint32_t experimenter == ?;
     of_octets_t data;
 };
 
diff --git a/openflow_input/standard-1.1 b/openflow_input/standard-1.1
index 1047127..a1127b1 100644
--- a/openflow_input/standard-1.1
+++ b/openflow_input/standard-1.1
@@ -443,7 +443,7 @@
     uint8_t type == 4;
     uint16_t length;
     uint32_t xid;
-    uint32_t experimenter;
+    uint32_t experimenter == ?;
     uint32_t subtype;
     of_octets_t data;
 };
@@ -742,7 +742,7 @@
 struct of_action_experimenter : of_action {
     uint16_t type == 65535;
     uint16_t len;
-    uint32_t experimenter;
+    uint32_t experimenter == ?;
     of_octets_t data;
 };
 
@@ -837,7 +837,7 @@
 struct of_instruction_experimenter : of_instruction {
     uint16_t type == 65535;
     uint16_t len;
-    uint32_t experimenter;
+    uint32_t experimenter == ?;
     of_octets_t data;
 };
 
@@ -1327,7 +1327,7 @@
     uint16_t stats_type == 0xffff;
     uint16_t flags;
     pad(4);
-    uint32_t experimenter;
+    uint32_t experimenter == ?;
     pad(4);
     of_octets_t data;
 };
@@ -1340,7 +1340,7 @@
     uint16_t stats_type == 0xffff;
     uint16_t flags;
     pad(4);
-    uint32_t experimenter;
+    uint32_t experimenter == ?;
     pad(4);
     of_octets_t data;
 };
diff --git a/openflow_input/standard-1.2 b/openflow_input/standard-1.2
index e4c8ec2..bfa9a64 100644
--- a/openflow_input/standard-1.2
+++ b/openflow_input/standard-1.2
@@ -483,7 +483,7 @@
     uint8_t type == 4;
     uint16_t length;
     uint32_t xid;
-    uint32_t experimenter;
+    uint32_t experimenter == ?;
     uint32_t subtype;
     of_octets_t data;
 };
@@ -699,7 +699,7 @@
 struct of_action_experimenter : of_action {
     uint16_t type == 65535;
     uint16_t len;
-    uint32_t experimenter;
+    uint32_t experimenter == ?;
     of_octets_t data;
 };
 
@@ -753,7 +753,7 @@
 struct of_instruction_experimenter : of_instruction {
     uint16_t type == 65535;
     uint16_t len;
-    uint32_t experimenter;
+    uint32_t experimenter == ?;
     of_octets_t data;
 };
 
@@ -1317,7 +1317,7 @@
     uint16_t stats_type == 0xffff;
     uint16_t flags;
     pad(4);
-    uint32_t experimenter;
+    uint32_t experimenter == ?;
     uint32_t subtype;
     of_octets_t data;
 };
@@ -1330,7 +1330,7 @@
     uint16_t stats_type == 0xffff;
     uint16_t flags;
     pad(4);
-    uint32_t experimenter;
+    uint32_t experimenter == ?;
     uint32_t subtype;
     of_octets_t data;
 };
@@ -1363,7 +1363,7 @@
     uint16_t type == 65535;
     uint16_t len;
     pad(4);
-    uint32_t experimenter;
+    uint32_t experimenter == ?;
     pad(4);
     of_octets_t data;
 };
diff --git a/openflow_input/standard-1.3 b/openflow_input/standard-1.3
index b9c5475..119e7a4 100644
--- a/openflow_input/standard-1.3
+++ b/openflow_input/standard-1.3
@@ -608,7 +608,7 @@
     uint8_t type == 4;
     uint16_t length;
     uint32_t xid;
-    uint32_t experimenter;
+    uint32_t experimenter == ?;
     uint32_t subtype;
     of_octets_t data;
 };
@@ -833,7 +833,7 @@
 struct of_action_experimenter : of_action {
     uint16_t type == 65535;
     uint16_t len;
-    uint32_t experimenter;
+    uint32_t experimenter == ?;
     of_octets_t data;
 };
 
@@ -905,7 +905,7 @@
 struct of_instruction_experimenter : of_instruction {
     uint16_t type == 65535;
     uint16_t len;
-    uint32_t experimenter;
+    uint32_t experimenter == ?;
     of_octets_t data;
 };
 
@@ -1177,7 +1177,8 @@
     uint16_t priority;
     uint16_t idle_timeout;
     uint16_t hard_timeout;
-    pad(6);
+    uint16_t flags;
+    pad(4);
     uint64_t cookie;
     uint64_t packet_count;
     uint64_t byte_count;
@@ -1770,7 +1771,7 @@
 };
 
 struct of_experimenter_multipart_header {
-    uint32_t experimenter;
+    uint32_t experimenter == ?;
     uint32_t subtype;
 };
 
@@ -1802,7 +1803,7 @@
     uint16_t type == 65535;
     uint16_t len;
     pad(4);
-    uint32_t experimenter;
+    uint32_t experimenter == ?;
     pad(4);
     of_octets_t data;
 };
diff --git a/py_gen/codegen.py b/py_gen/codegen.py
index 6570938..540d212 100644
--- a/py_gen/codegen.py
+++ b/py_gen/codegen.py
@@ -54,13 +54,10 @@
 # Create intermediate representation, extended from the LOXI IR
 # HACK the oftype member attribute is replaced with an OFType instance
 def build_ofclasses(version):
-    blacklist = ["of_experimenter", "of_action_experimenter"]
     ofclasses = []
     for ofclass in of_g.ir[version].classes:
         cls = ofclass.name
-        if type_maps.class_is_virtual(cls):
-            continue
-        if cls in blacklist:
+        if ofclass.virtual:
             continue
 
         members = []
diff --git a/py_gen/templates/message.py b/py_gen/templates/message.py
index 6754b94..7158545 100644
--- a/py_gen/templates/message.py
+++ b/py_gen/templates/message.py
@@ -226,11 +226,6 @@
     const.OFPST_TABLE : table_stats_reply.unpack,
     const.OFPST_PORT : port_stats_reply.unpack,
     const.OFPST_QUEUE : queue_stats_reply.unpack,
-:: if version < of_g.VERSION_1_1:
-    const.OFPST_VENDOR : experimenter_stats_reply.unpack,
-:: else:
-    const.OFPST_EXPERIMENTER : experimenter_stats_reply.unpack,
-:: #endif
 :: if version >= of_g.VERSION_1_1:
     const.OFPST_GROUP : group_stats_reply.unpack,
     const.OFPST_GROUP_DESC : group_desc_stats_reply.unpack,
@@ -247,11 +242,6 @@
     const.OFPST_TABLE : table_stats_request.unpack,
     const.OFPST_PORT : port_stats_request.unpack,
     const.OFPST_QUEUE : queue_stats_request.unpack,
-:: if version < of_g.VERSION_1_1:
-    const.OFPST_VENDOR : experimenter_stats_request.unpack,
-:: else:
-    const.OFPST_EXPERIMENTER : experimenter_stats_request.unpack,
-:: #endif
 :: if version >= of_g.VERSION_1_1:
     const.OFPST_GROUP : group_stats_request.unpack,
     const.OFPST_GROUP_DESC : group_desc_stats_request.unpack,