diff --git a/tests/dart2js/29130_test.dart b/tests/dart2js/29130_test.dart
index 4426f262634..6766e0c4f27 100644
--- a/tests/dart2js/29130_test.dart
+++ b/tests/dart2js/29130_test.dart
@@ -20,7 +20,11 @@ class A {
 
 // interface scenario: we shouldn't trace B
 abstract class B implements A {
-  factory B() => null as dynamic;
+  factory B() => DummyB();
+}
+
+class DummyB implements B {
+  call() {}
 }
 
 // mixin scenario: we should trace C, but we should trace _C