diff --git a/tests/lib/isolate/spawn_uri_nested_vm_test.dart b/tests/lib/isolate/spawn_uri_nested_vm_test.dart
index 087b5fc4747..0847cf69ee7 100644
--- a/tests/lib/isolate/spawn_uri_nested_vm_test.dart
+++ b/tests/lib/isolate/spawn_uri_nested_vm_test.dart
@@ -12,12 +12,19 @@ import 'dart:isolate';
 import 'package:async_helper/async_minitest.dart';
 
 main() {
-  test('isolate fromUri - nested send and reply', () {
-    ReceivePort port = new ReceivePort();
-    Isolate.spawnUri(Uri.parse('spawn_uri_nested_child1_vm_isolate.dart'), [], [
-      [1, 2],
-      port.sendPort
-    ]);
+  test('isolate fromUri - nested send and reply', () async {
+    final port = ReceivePort();
+    final exitPort = ReceivePort();
+    Isolate.spawnUri(
+        Uri.parse('spawn_uri_nested_child1_vm_isolate.dart'),
+        [],
+        [
+          [1, 2],
+          port.sendPort
+        ],
+        onExit: exitPort.sendPort);
     port.first.then(expectAsync((result) => print(result)));
+    // ensure main isolate doesn't exit before child isolate exits
+    await exitPort.first;
   });
 }
diff --git a/tests/lib_2/isolate/spawn_uri_nested_vm_test.dart b/tests/lib_2/isolate/spawn_uri_nested_vm_test.dart
index 423821db026..81e5882123a 100644
--- a/tests/lib_2/isolate/spawn_uri_nested_vm_test.dart
+++ b/tests/lib_2/isolate/spawn_uri_nested_vm_test.dart
@@ -14,12 +14,19 @@ import 'dart:isolate';
 import 'package:async_helper/async_minitest.dart';
 
 main() {
-  test('isolate fromUri - nested send and reply', () {
-    ReceivePort port = new ReceivePort();
-    Isolate.spawnUri(Uri.parse('spawn_uri_nested_child1_vm_isolate.dart'), [], [
-      [1, 2],
-      port.sendPort
-    ]);
+  test('isolate fromUri - nested send and reply', () async {
+    final port = ReceivePort();
+    final exitPort = ReceivePort();
+    Isolate.spawnUri(
+        Uri.parse('spawn_uri_nested_child1_vm_isolate.dart'),
+        [],
+        [
+          [1, 2],
+          port.sendPort
+        ],
+        onExit: exitPort.sendPort);
     port.first.then(expectAsync((result) => print(result)));
+    // ensure main isolate doesn't exit before child isolate exits
+    await exitPort.first;
   });
 }