diff --git a/dnstap.proto b/dnstap.proto
index dfc8ad4..c2c66a2 100644
--- a/dnstap.proto
+++ b/dnstap.proto
@@ -67,6 +67,14 @@ enum SocketProtocol {
     DOQ = 7;         // DNS over QUIC (RFC 9250)
 }
 
+// HttpProtocol: the HTTP protocol version used to transport a DNS message over
+// an HTTP-based protocol such as DNS over HTTPS.
+enum HttpProtocol {
+    HTTP1 = 1; // HTTP/1
+    HTTP2 = 2; // HTTP/2
+    HTTP3 = 3; // HTTP/3
+}
+
 // Policy: information about any name server operator policy
 // applied to the processing of a DNS message.
 message Policy {
@@ -285,6 +293,10 @@ message Message {
 
     // Operator policy applied to the processing of this message, if any.
     optional Policy             policy = 15;
+
+    // One of the HttpProtocol values described above. This field should only be
+    // set if socket_protocol is set to DOH.
+    optional HttpProtocol       http_protocol = 16;
 }
 
 // All fields except for 'type' in the Message schema are optional.