diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index daeac27..2f354bb 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -1595,6 +1595,9 @@
                                     nullptr);
                         }
                     } else {
+                        // WM changes displayDevice->layerStack upon sleep/awake.
+                        // Here we make sure we delete the HWC layers even if
+                        // WM changed their layer stack.
                         layer->setHwcLayer(displayDevice->getHwcDisplayId(),
                                 nullptr);
                     }