diff --git a/lib/ns/tests/listenlist_test.c b/lib/ns/tests/listenlist_test.c
index 78ca786d8f..55fcc45741 100644
--- a/lib/ns/tests/listenlist_test.c
+++ b/lib/ns/tests/listenlist_test.c
@@ -28,6 +28,7 @@
 
 #include <isc/list.h>
 #include <isc/print.h>
+#include <isc/random.h>
 
 #include <dns/acl.h>
 
@@ -60,13 +61,14 @@ _teardown(void **state) {
 static void
 ns_listenlist_default_test(void **state) {
 	isc_result_t result;
+	in_port_t port = 5300 + isc_random8();
 	ns_listenlist_t *list = NULL;
 	ns_listenelt_t *elt;
 	int count;
 
 	UNUSED(state);
 
-	result = ns_listenlist_default(mctx, 5300, -1, false, &list);
+	result = ns_listenlist_default(mctx, port, -1, false, &list);
 	assert_int_equal(result, ISC_R_SUCCESS);
 	assert_non_null(list);
 
@@ -93,7 +95,7 @@ ns_listenlist_default_test(void **state) {
 
 	ns_listenlist_detach(&list);
 
-	result = ns_listenlist_default(mctx, 5300, -1, true, &list);
+	result = ns_listenlist_default(mctx, port, -1, true, &list);
 	assert_int_equal(result, ISC_R_SUCCESS);
 
 	assert_false(ISC_LIST_EMPTY(list->elts));
diff --git a/lib/ns/tests/nstest.c b/lib/ns/tests/nstest.c
index 6a6bd45e72..d4314693d2 100644
--- a/lib/ns/tests/nstest.c
+++ b/lib/ns/tests/nstest.c
@@ -215,6 +215,7 @@ scan_interfaces(isc_task_t *task, isc_event_t *event) {
 static isc_result_t
 create_managers(void) {
 	isc_result_t result;
+	in_port_t port = 5300 + isc_random8();
 	ns_listenlist_t *listenon = NULL;
 	isc_event_t *event = NULL;
 	ncpus = isc_os_ncpus();
@@ -238,7 +239,7 @@ create_managers(void) {
 				     socketmgr, nm, dispatchmgr, maintask,
 				     ncpus, NULL, &interfacemgr));
 
-	CHECK(ns_listenlist_default(mctx, 5300, -1, true, &listenon));
+	CHECK(ns_listenlist_default(mctx, port, -1, true, &listenon));
 	ns_interfacemgr_setlistenon4(interfacemgr, listenon);
 	ns_listenlist_detach(&listenon);