diff --git a/include/gui/IGraphicBufferProducer.h b/include/gui/IGraphicBufferProducer.h
index 9677962..033c727 100644
--- a/include/gui/IGraphicBufferProducer.h
+++ b/include/gui/IGraphicBufferProducer.h
@@ -105,7 +105,8 @@
     // and height of the window and current transform applied to buffers,
     // respectively.
 
-    struct QueueBufferInput : public Flattenable {
+    struct QueueBufferInput : public Flattenable<QueueBufferInput> {
+        friend class Flattenable<QueueBufferInput>;
         inline QueueBufferInput(const Parcel& parcel);
         inline QueueBufferInput(int64_t timestamp,
                 const Rect& crop, int scalingMode, uint32_t transform, bool async,
@@ -123,13 +124,11 @@
             *outFence = fence;
         }
 
-        // Flattenable interface
-        virtual size_t getFlattenedSize() const;
-        virtual size_t getFdCount() const;
-        virtual status_t flatten(void* buffer, size_t size,
-                int fds[], size_t count) const;
-        virtual status_t unflatten(void const* buffer, size_t size,
-                int fds[], size_t count);
+        // Flattenable protocol
+        size_t getFlattenedSize() const;
+        size_t getFdCount() const;
+        status_t flatten(void*& buffer, size_t& size, int*& fds, size_t& count) const;
+        status_t unflatten(void const*& buffer, size_t& size, int const*& fds, size_t& count);
 
     private:
         int64_t timestamp;
diff --git a/include/gui/Sensor.h b/include/gui/Sensor.h
index 2af2307..9197372 100644
--- a/include/gui/Sensor.h
+++ b/include/gui/Sensor.h
@@ -70,8 +70,8 @@
 
     // LightFlattenable protocol
     inline bool isFixedSize() const { return false; }
-    size_t getSize() const;
-    status_t flatten(void* buffer) const;
+    size_t getFlattenedSize() const;
+    status_t flatten(void* buffer, size_t size) const;
     status_t unflatten(void const* buffer, size_t size);
 
 private: