diff --git a/libs/gui/aidl/android/gui/ISurfaceComposer.aidl b/libs/gui/aidl/android/gui/ISurfaceComposer.aidl
index a9977b0..b31b37b 100644
--- a/libs/gui/aidl/android/gui/ISurfaceComposer.aidl
+++ b/libs/gui/aidl/android/gui/ISurfaceComposer.aidl
@@ -54,10 +54,11 @@
      */
     void setPowerMode(IBinder display, int mode);
 
-    /* returns display statistics for a given display
+    /**
+     * Returns display statistics for a given display
      * intended to be used by the media framework to properly schedule
      * video frames */
-    DisplayStatInfo getDisplayStats(IBinder display);
+    DisplayStatInfo getDisplayStats(@nullable IBinder display);
 
      /**
      * Get transactional state of given display.