diff --git a/examples/ipsec-acc.p4 b/examples/ipsec-acc.p4
index fc2dd1a..1c4cd95 100644
--- a/examples/ipsec-acc.p4
+++ b/examples/ipsec-acc.p4
@@ -125,7 +125,8 @@ parser MainParserImpl(
     packet_in pkt,
     out   headers_t       hdr,
     inout main_metadata_t main_meta,
-    in    pna_main_parser_input_metadata_t istd)
+    in    pna_main_parser_input_metadata_t istd,
+    inout vendor_metadata_t vmeta)
 {
     bit<1> is_recirc = 0;
     bit<2>  ipsec_op = 0;
@@ -436,7 +437,8 @@ control MainControlImpl(
     inout headers_t       hdr,
     inout main_metadata_t main_meta,
     in    pna_main_input_metadata_t  istd,
-    inout pna_main_output_metadata_t ostd)
+    inout pna_main_output_metadata_t ostd,
+    inout vendor_metadata_t vmeta)
 {
     apply {
         if (main_meta.ipsec_decrypt_done == 1) {
@@ -451,7 +453,8 @@ control MainDeparserImpl(
     packet_out pkt,
     in    headers_t hdr,                // from main control
     in    main_metadata_t user_meta,    // from main control
-    in    pna_main_output_metadata_t ostd)
+    in    pna_main_output_metadata_t ostd,
+    inout vendor_metadata_t vmeta)
 {
     apply {
         pkt.emit(hdr.recirc_header);
diff --git a/examples/pna-demo-L2-one-table.p4 b/examples/pna-demo-L2-one-table.p4
index 45617aa..74e79bc 100644
--- a/examples/pna-demo-L2-one-table.p4
+++ b/examples/pna-demo-L2-one-table.p4
@@ -47,7 +47,8 @@ parser MainParserImpl(
     packet_in pkt,
     out   headers_t  hdr,
     inout metadata_t meta,
-    in    pna_main_parser_input_metadata_t istd)
+    in    pna_main_parser_input_metadata_t istd,
+    inout vendor_metadata_t vmeta)
 {
     state start {
         pkt.extract(hdr.eth);
@@ -59,7 +60,8 @@ control MainControlImpl(
     inout headers_t  hdr,
     inout metadata_t meta,
     in    pna_main_input_metadata_t  istd,
-    inout pna_main_output_metadata_t ostd)
+    inout pna_main_output_metadata_t ostd,
+    inout vendor_metadata_t vmeta)
 {
     action drop () {
         drop_packet();
@@ -99,7 +101,8 @@ control MainDeparserImpl(
     packet_out pkt,
     in    headers_t hdr,
     in    metadata_t meta,
-    in    pna_main_output_metadata_t ostd)
+    in    pna_main_output_metadata_t ostd,
+    inout vendor_metadata_t vmeta)
 {
     apply {
         pkt.emit(hdr.eth);
diff --git a/examples/pna-demo-L2-two-tables.p4 b/examples/pna-demo-L2-two-tables.p4
index bafe8fa..945768e 100644
--- a/examples/pna-demo-L2-two-tables.p4
+++ b/examples/pna-demo-L2-two-tables.p4
@@ -47,7 +47,8 @@ parser MainParserImpl(
     packet_in pkt,
     out   headers_t  hdr,
     inout metadata_t meta,
-    in    pna_main_parser_input_metadata_t istd)
+    in    pna_main_parser_input_metadata_t istd,
+    inout vendor_metadata_t vmeta)
 {
     state start {
         pkt.extract(hdr.eth);
@@ -59,7 +60,8 @@ control MainControlImpl(
     inout headers_t  hdr,
     inout metadata_t meta,
     in    pna_main_input_metadata_t  istd,
-    inout pna_main_output_metadata_t ostd)
+    inout pna_main_output_metadata_t ostd,
+    inout vendor_metadata_t vmeta)
 {
     action drop () {
         drop_packet();
@@ -106,7 +108,8 @@ control MainDeparserImpl(
     packet_out pkt,
     in    headers_t hdr,
     in    metadata_t meta,
-    in    pna_main_output_metadata_t ostd)
+    in    pna_main_output_metadata_t ostd,
+    inout vendor_metadata_t vmeta)
 {
     apply {
         pkt.emit(hdr.eth);
diff --git a/examples/pna-demo-last-forwarding-action-wins.p4 b/examples/pna-demo-last-forwarding-action-wins.p4
index f480d33..acc87db 100644
--- a/examples/pna-demo-last-forwarding-action-wins.p4
+++ b/examples/pna-demo-last-forwarding-action-wins.p4
@@ -52,7 +52,8 @@ parser MainParserImpl(
     packet_in pkt,
     out   headers_t  hdr,
     inout metadata_t meta,
-    in    pna_main_parser_input_metadata_t istd)
+    in    pna_main_parser_input_metadata_t istd,
+    inout vendor_metadata_t vmeta)
 {
     state start {
         pkt.extract(hdr.eth);
@@ -64,7 +65,8 @@ control MainControlImpl(
     inout headers_t  hdr,
     inout metadata_t meta,
     in    pna_main_input_metadata_t  istd,
-    inout pna_main_output_metadata_t ostd)
+    inout pna_main_output_metadata_t ostd,
+    inout vendor_metadata_t vmeta)
 {
     action my_drop () {
         drop_packet();
@@ -139,7 +141,8 @@ control MainDeparserImpl(
     packet_out pkt,
     in    headers_t hdr,
     in    metadata_t meta,
-    in    pna_main_output_metadata_t ostd)
+    in    pna_main_output_metadata_t ostd,
+    inout vendor_metadata_t vmeta)
 {
     apply {
         pkt.emit(hdr.eth);
diff --git a/examples/pna-example-tcp-connection-tracking.p4 b/examples/pna-example-tcp-connection-tracking.p4
index 8faf9fb..b83f3b0 100644
--- a/examples/pna-example-tcp-connection-tracking.p4
+++ b/examples/pna-example-tcp-connection-tracking.p4
@@ -95,7 +95,8 @@ parser MainParserImpl(
     packet_in pkt,
     out   headers_t  hdr,
     inout metadata_t meta,
-    in    pna_main_parser_input_metadata_t istd)
+    in    pna_main_parser_input_metadata_t istd,
+    inout vendor_metadata_t vmeta)
 {
     state start {
         pkt.extract(hdr.eth);
@@ -124,7 +125,8 @@ control MainControlImpl(
     inout headers_t  hdr,
     inout metadata_t meta,
     in    pna_main_input_metadata_t  istd,
-    inout pna_main_output_metadata_t ostd)
+    inout pna_main_output_metadata_t ostd,
+    inout vendor_metadata_t vmeta)
 {
     action drop () {
         drop_packet();
@@ -339,7 +341,8 @@ control MainDeparserImpl(
     packet_out pkt,
     in    headers_t hdr,
     in    metadata_t meta,
-    in    pna_main_output_metadata_t ostd)
+    in    pna_main_output_metadata_t ostd,
+    inout vendor_metadata_t vmeta)
 {
     apply {
         pkt.emit(hdr.eth);
diff --git a/examples/pna-example-template.p4 b/examples/pna-example-template.p4
index b06dbe5..fb9c1e5 100644
--- a/examples/pna-example-template.p4
+++ b/examples/pna-example-template.p4
@@ -79,7 +79,8 @@ parser MainParserImpl(
     packet_in pkt,
     out   headers_t       hdr,
     inout main_metadata_t main_meta,
-    in    pna_main_parser_input_metadata_t istd)
+    in    pna_main_parser_input_metadata_t istd,
+    inout vendor_metadata_t vmeta)
 {
     state start {
         pkt.extract(hdr.ethernet);
@@ -99,7 +100,8 @@ control MainControlImpl(
     inout headers_t       hdr,           // from main parser
     inout main_metadata_t user_meta,     // from main parser, to "next block"
     in    pna_main_input_metadata_t  istd,
-    inout pna_main_output_metadata_t ostd)
+    inout pna_main_output_metadata_t ostd,
+    inout vendor_metadata_t vmeta)
 {
     Counter<ByteCounter_t, PortId_t>(NUM_PORTS, PNA_CounterType_t.BYTES)
         port_bytes_in;
@@ -139,7 +141,8 @@ control MainDeparserImpl(
     packet_out pkt,
     in    headers_t hdr,                // from main control
     in    main_metadata_t user_meta,    // from main control
-    in    pna_main_output_metadata_t ostd)
+    in    pna_main_output_metadata_t ostd,
+    inout vendor_metadata_t vmeta)
 {
     apply {
         pkt.emit(hdr.ethernet);
diff --git a/pna.p4 b/pna.p4
index c1b7666..6e93f3a 100644
--- a/pna.p4
+++ b/pna.p4
@@ -847,6 +847,17 @@ extern T SelectByDirection<T>(
     in T from_host_value);
 
 
+// BEGIN:vendor_metadata_struct
+// The contents of this struct are _not_ defined by the PNA
+// specification.  By design, it is intended to be unique from one
+// target device to another.  The intent is to be a standard place to
+// put intrinsic metadata that vendors wish to make accessible in
+// their devices, for which there is not yet general agreement that
+// the field should be considered part of the PNA intrinsic metadata.
+
+struct vendor_metadata_t {
+}
+// END:vendor_metadata_struct
 
 
 // BEGIN:Programmable_blocks
@@ -854,19 +865,22 @@ parser MainParserT<MH, MM>(
     packet_in pkt,
     out   MH main_hdr,
     inout MM main_user_meta,
-    in    pna_main_parser_input_metadata_t istd);
+    in    pna_main_parser_input_metadata_t istd,
+    inout vendor_metadata_t vmeta);
 
 control MainControlT<MH, MM>(
     inout MH main_hdr,
     inout MM main_user_meta,
     in    pna_main_input_metadata_t  istd,
-    inout pna_main_output_metadata_t ostd);
+    inout pna_main_output_metadata_t ostd,
+    inout vendor_metadata_t vmeta);
 
 control MainDeparserT<MH, MM>(
     packet_out pkt,
     in    MH main_hdr,
     in    MM main_user_meta,
-    in    pna_main_output_metadata_t ostd);
+    in    pna_main_output_metadata_t ostd,
+    inout vendor_metadata_t vmeta);
 
 package PNA_NIC<MH, MM>(
     MainParserT<MH, MM> main_parser,