diff --git a/stable/android/os/IUpdateEngineStable.aidl b/stable/android/os/IUpdateEngineStable.aidl
index b3b6674..5aa15ba 100644
--- a/stable/android/os/IUpdateEngineStable.aidl
+++ b/stable/android/os/IUpdateEngineStable.aidl
@@ -21,6 +21,10 @@
 
 /**
  * The stable interface exposed by the update engine daemon.
+ *
+ * WARNING: this interface exposes less capabilities than IUpdateEngine,
+ * for instance, not having a cancel method. This is relied on for
+ * security.
  */
 interface IUpdateEngineStable {
   /**