diff --git a/libavformat/mov.c b/libavformat/mov.c
index b5d3e93ad5..c2d2a07893 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -2017,6 +2017,11 @@ static void mov_build_index(MOVContext *mov, AVStream *st)
                         rap_group_index++;
                     }
                 }
+                if (sc->keyframe_absent
+                    && !sc->stps_count
+                    && !rap_group_present
+                    && st->codec->codec_type == AVMEDIA_TYPE_AUDIO)
+                     keyframe = 1;
                 if (keyframe)
                     distance = 0;
                 sample_size = sc->alt_sample_size > 0 ? sc->alt_sample_size : sc->sample_sizes[current_sample];