diff --git a/httpd.c b/httpd.c
index f130e529..6fa901d3 100644
--- a/httpd.c
+++ b/httpd.c
@@ -272,8 +272,8 @@ void httpd_server_poll(struct sched_ent *alarm)
 	}
 	current_httpd_requests = request;
 	++current_httpd_request_count;
-	request->payload_status = INVALID_RHIZOME_PAYLOAD_STATUS;
-	request->bundle_status = INVALID_RHIZOME_BUNDLE_STATUS;
+	request->payload_status = INVALID_RHIZOME_PAYLOAD_STATUS; // will cause FATAL unless set
+	request->bundle_status = INVALID_RHIZOME_BUNDLE_STATUS; // will cause FATAL unless set
 	if (peerip)
 	  request->http.client_sockaddr_in = *peerip;
 	request->http.uuid = http_request_uuid_counter;
diff --git a/rhizome.h b/rhizome.h
index a53dea12..aeeb1b4f 100644
--- a/rhizome.h
+++ b/rhizome.h
@@ -414,6 +414,8 @@ enum rhizome_bundle_status {
     RHIZOME_BUNDLE_STATUS_BUSY = 9, // the database is currently busy
 };
 
+// Useful for initialising a variable then checking later that it was set to a
+// valid value (typically FATAL if not).
 #define INVALID_RHIZOME_BUNDLE_STATUS ((enum rhizome_bundle_status)-2)
 
 const char *rhizome_bundle_status_message(enum rhizome_bundle_status);
@@ -431,6 +433,8 @@ enum rhizome_payload_status {
     RHIZOME_PAYLOAD_STATUS_EVICTED = 7, // other payloads in our store are more important
 };
 
+// Useful for initialising a variable then checking later that it was set to a
+// valid value (typically FATAL if not).
 #define INVALID_RHIZOME_PAYLOAD_STATUS ((enum rhizome_payload_status)-2)
 
 const char *rhizome_payload_status_message(enum rhizome_payload_status);