diff --git a/core/java/android/provider/SearchIndexableData.java b/core/java/android/provider/SearchIndexableData.java
index 5e0a76de8d27a..a60be5363d626 100644
--- a/core/java/android/provider/SearchIndexableData.java
+++ b/core/java/android/provider/SearchIndexableData.java
@@ -56,6 +56,8 @@ public abstract class SearchIndexableData {
     /**
      * The key for the data. This is application specific. Should be unique per data as the data
      * should be able to be retrieved by the key.
+     * <p/>
+     * This is required for indexing to work.
      */
     public String key;