diff --git a/genlibtokenlookup.py b/genlibtokenlookup.py
index 267a30b4..9477d07d 100755
--- a/genlibtokenlookup.py
+++ b/genlibtokenlookup.py
@@ -67,6 +67,7 @@ HEADERS = [
     ('keep-alive',None),
     ('proxy-connection', None),
     ('upgrade', None),
+    (':protocol', None),
 ]
 
 def to_enum_hd(k):
diff --git a/lib/nghttp2_hd.c b/lib/nghttp2_hd.c
index 82cc23de..a61f0d47 100644
--- a/lib/nghttp2_hd.c
+++ b/lib/nghttp2_hd.c
@@ -271,6 +271,15 @@ static int32_t lookup_token(const uint8_t *name, size_t namelen) {
       break;
     }
     break;
+  case 9:
+    switch (name[8]) {
+    case 'l':
+      if (memeq(":protoco", name, 8)) {
+        return NGHTTP2_TOKEN__PROTOCOL;
+      }
+      break;
+    }
+    break;
   case 10:
     switch (name[9]) {
     case 'e':
diff --git a/lib/nghttp2_hd.h b/lib/nghttp2_hd.h
index c64a1f2b..14ae9807 100644
--- a/lib/nghttp2_hd.h
+++ b/lib/nghttp2_hd.h
@@ -111,6 +111,7 @@ typedef enum {
   NGHTTP2_TOKEN_KEEP_ALIVE,
   NGHTTP2_TOKEN_PROXY_CONNECTION,
   NGHTTP2_TOKEN_UPGRADE,
+  NGHTTP2_TOKEN__PROTOCOL,
 } nghttp2_token;
 
 struct nghttp2_hd_entry;