diff --git a/include/haproxy/h1.h b/include/haproxy/h1.h
index 25d3e5fd0..84c9d9217 100644
--- a/include/haproxy/h1.h
+++ b/include/haproxy/h1.h
@@ -98,7 +98,7 @@ enum h1m_state {
 #define H1_MF_UPG_WEBSOCKET     0x00008000 // Set for a Websocket upgrade handshake
 #define H1_MF_TE_CHUNKED        0x00010000 // T-E "chunked"
 #define H1_MF_TE_OTHER          0x00020000 // T-E other than supported ones found (only "chunked" is supported for now)
-/* unused: 0x00040000 */
+#define H1_MF_UPG_HDR           0x00040000 // non-empty Upgrapde header found
 #define H1_MF_NOT_HTTP           0x00080000 // Not an HTTP message (e.g "RTSP", only possible if invalid message are accepted)
 /* Mask to use to reset H1M flags when we restart headers parsing.
  *
diff --git a/src/h1.c b/src/h1.c
index 98bb492b2..7a88fb192 100644
--- a/src/h1.c
+++ b/src/h1.c
@@ -316,6 +316,9 @@ void h1_parse_upgrade_header(struct h1m *h1m, struct ist *value)
 	  skip_val:
 		word.ptr = p = n;
 	}
+
+	if (istlen(*value))
+		h1m->flags |= H1_MF_UPG_HDR;
 }
 
 /* Macros used in the HTTP/1 parser, to check for the expected presence of