diff --git a/CHANGES b/CHANGES
index 30afe3d3f9..6e8edb7cec 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 f8433e224d..ee6a5142aa 100644
--- a/lib/dns/request.c
+++ b/lib/dns/request.c
@@ -445,10 +445,11 @@ req_send(dns_request_t *request, isc_task_t *task, isc_sockaddr_t *address) {
 		sendevent->dscp = request->dscp;
 	}
 
+	request->flags |= DNS_REQUEST_F_SENDING;
 	result = isc_socket_sendto2(sock, &r, task, address, NULL,
 				    sendevent, 0);
-	if (result == ISC_R_SUCCESS)
-		request->flags |= DNS_REQUEST_F_SENDING;
+	if (result != ISC_R_SUCCESS)
+		request->flags &= ~DNS_REQUEST_F_SENDING;
 	return (result);
 }