diff --git a/tests/foo/1.0/IFoo.hal b/tests/foo/1.0/IFoo.hal
index c06fc05..ea69e1e 100644
--- a/tests/foo/1.0/IFoo.hal
+++ b/tests/foo/1.0/IFoo.hal
@@ -117,6 +117,9 @@
 
     haveAVectorOfGenericInterfaces(vec<interface> in)
         generates (vec<interface> out);
+
+    echoNullInterface(IFooCallback cb) generates (bool receivedNull, IFooCallback cb);
+
     createMyHandle() generates (MyHandle h);
     createHandles(uint32_t size) generates (vec<handle> handles);
     closeHandles();