diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index bd211975767905e1d3a19bac5a9f8e162e1bf45f..f72058988f139cfe4e18b760fc21044544869846 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -2937,6 +2937,13 @@ typedef struct AVHWAccel {
      */
     int capabilities;
 
+    /*****************************************************************
+     * No fields below this line are part of the public API. They
+     * may not be used outside of libavcodec and can be changed and
+     * removed at will.
+     * New public fields should be added right above.
+     *****************************************************************
+     */
     struct AVHWAccel *next;
 
     /**