diff --git a/tests/lazy/1.1/ILazy.hal b/tests/lazy/1.1/ILazy.hal
index a15e0e3..b0a6a2a 100644
--- a/tests/lazy/1.1/ILazy.hal
+++ b/tests/lazy/1.1/ILazy.hal
@@ -18,4 +18,12 @@
 
 import android.hardware.tests.lazy@1.0;
 
-interface ILazy extends @1.0::ILazy {};
+interface ILazy extends @1.0::ILazy {
+    /**
+     * Ask the process hosting the service to install a callback that notifies
+     * it when the number of active (i.e. with clients) services changes.
+     * For testing purposes, this callback exercises the code to unregister/re-register
+     * the services and eventually shuts down the process.
+     */
+    setCustomActiveServicesCountCallback();
+};