diff --git a/openflow_input/standard-1.3 b/openflow_input/standard-1.3
index b9c5475..3e85338 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;
 };
 
@@ -1770,7 +1770,7 @@
 };
 
 struct of_experimenter_multipart_header {
-    uint32_t experimenter;
+    uint32_t experimenter == ?;
     uint32_t subtype;
 };
 
@@ -1802,7 +1802,7 @@
     uint16_t type == 65535;
     uint16_t len;
     pad(4);
-    uint32_t experimenter;
+    uint32_t experimenter == ?;
     pad(4);
     of_octets_t data;
 };