diff --git a/CHANGES b/CHANGES
index 8467737d2f..ca46cdf3f1 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,6 @@
+4535.	[bug]		Address race condition in setting / testing of
+			DNS_REQUEST_F_SENDING. [RT #43889]
+
 4534.	[bug]		Only set RD, RA and CD in QUERY responses. [RT #43879]
 
 4533.	[bug]		dns_client_update should terminate on prerequisite
diff --git a/lib/dns/request.c b/lib/dns/request.c
index 639ec5c8b8..4dc0e07d93 100644
--- a/lib/dns/request.c
+++ b/lib/dns/request.c
@@ -439,10 +439,11 @@ req_send(dns_request_t *request, isc_task_t *task, isc_sockaddr_t *address) {
 	 * as we do in resolver.c, but we prefer implementation simplicity
 	 * at this moment.
 	 */
+	request->flags |= DNS_REQUEST_F_SENDING;
 	result = isc_socket_sendto(sock, &r, task, req_senddone,
 				  request, address, NULL);
-	if (result == ISC_R_SUCCESS)
-		request->flags |= DNS_REQUEST_F_SENDING;
+	if (result != ISC_R_SUCCESS)
+		request->flags &= ~DNS_REQUEST_F_SENDING;
 	return (result);
 }