diff --git a/lib/dns/tests/dispatch_test.c b/lib/dns/tests/dispatch_test.c
index 9785fbfbae8caf529179d7c3645b1cd441b4cce5..3467fa6923949d32c4f1024631408a9d7d15db4f 100644
--- a/lib/dns/tests/dispatch_test.c
+++ b/lib/dns/tests/dispatch_test.c
@@ -27,6 +27,7 @@
 
 #include <isc/app.h>
 #include <isc/buffer.h>
+#include <isc/refcount.h>
 #include <isc/socket.h>
 #include <isc/task.h>
 #include <isc/timer.h>
@@ -212,27 +213,20 @@ nameserver(isc_task_t *task, isc_event_t *event) {
 
 static dns_dispatch_t *dispatch = NULL;
 static dns_dispentry_t *dispentry = NULL;
-static bool first = true;
-static isc_mutex_t lock;
+static atomic_bool first = ATOMIC_VAR_INIT(true);
 static isc_sockaddr_t local;
-static unsigned int responses = 0;
+static isc_refcount_t responses;
 
 static void
 response(isc_task_t *task, isc_event_t *event) {
 	dns_dispatchevent_t *devent = (dns_dispatchevent_t *)event;
-	isc_result_t result;
-	bool wasfirst;
+	bool exp_true = true;
 
 	UNUSED(task);
 
-	LOCK(&lock);
-	wasfirst = first;
-	first = false;
-	responses++;
-	UNLOCK(&lock);
-
-	if (wasfirst) {
-		result = dns_dispatch_getnext(dispentry, &devent);
+	isc_refcount_increment(&responses);
+	if (atomic_compare_exchange_strong(&first, &exp_true, false)) {
+		isc_result_t result = dns_dispatch_getnext(dispentry, &devent);
 		assert_int_equal(result, ISC_R_SUCCESS);
 	} else {
 		dns_dispatch_removeresponse(&dispentry, &devent);
@@ -267,7 +261,7 @@ dispatch_getnext(void **state) {
 
 	UNUSED(state);
 
-	isc_mutex_init(&lock);
+	isc_refcount_init(&responses, 0);
 
 	result = isc_task_create(taskmgr, 0, &task);
 	assert_int_equal(result, ISC_R_SUCCESS);
@@ -298,7 +292,6 @@ dispatch_getnext(void **state) {
 	result = isc_socket_getsockname(sock, &local);
 	assert_int_equal(result, ISC_R_SUCCESS);
 
-	first = true;
 	region.base = rbuf;
 	region.length = sizeof(rbuf);
 	result = isc_socket_recv(sock, &region, 1, task, nameserver, sock);
@@ -320,7 +313,7 @@ dispatch_getnext(void **state) {
 	result = isc_app_run();
 	assert_int_equal(result, ISC_R_SUCCESS);
 
-	assert_int_equal(responses, 2);
+	assert_int_equal(isc_refcount_current(&responses), 2);
 
 	/*
 	 * Shutdown nameserver.