diff --git a/libavformat/mov.c b/libavformat/mov.c
index 127aec1d1d..e487e59634 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -4338,8 +4338,8 @@ static int mov_read_sidx(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     uint8_t version;
     unsigned i, track_id;
     AVStream *st = NULL;
-    AVStream *ref_st;
-    MOVStreamContext *sc, *ref_sc;
+    AVStream *ref_st = NULL;
+    MOVStreamContext *sc, *ref_sc = NULL;
     MOVFragmentIndex *index = NULL;
     MOVFragmentIndex **tmp;
     AVRational timescale;