diff --git a/libavformat/avformat.h b/libavformat/avformat.h
index 21e505d2ae..ae70cc88ec 100644
--- a/libavformat/avformat.h
+++ b/libavformat/avformat.h
@@ -814,6 +814,9 @@ typedef struct AVIndexEntry {
                                * is known
                                */
 #define AVINDEX_KEYFRAME 0x0001
+#define AVINDEX_DISCARD_FRAME  0x0002    /**
+                                          * Flag is used to indicate which frame should be discarded after decoding.
+                                          */
     int flags:2;
     int size:30; //Yeah, trying to keep the size of this small to reduce memory requirements (it is 24 vs. 32 bytes due to possible 8-byte alignment).
     int min_distance;         /**< Minimum distance between this and the previous keyframe, used to avoid unneeded searching. */