diff --git a/libavformat/mov.c b/libavformat/mov.c
index ce61250eac..d3bd2280a2 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -851,6 +851,7 @@ static int mov_read_smi(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     // currently SVQ3 decoder expect full STSD header - so let's fake it
     // this should be fixed and just SMI header should be passed
     av_free(st->codec->extradata);
+    st->codec->extradata_size = 0;
     st->codec->extradata = av_mallocz(atom.size + 0x5a + FF_INPUT_BUFFER_PADDING_SIZE);
     if (!st->codec->extradata)
         return AVERROR(ENOMEM);
@@ -987,6 +988,7 @@ static int mov_read_wave(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     if (st->codec->codec_id == CODEC_ID_QDM2 || st->codec->codec_id == CODEC_ID_QDMC) {
         // pass all frma atom to codec, needed at least for QDMC and QDM2
         av_free(st->codec->extradata);
+        st->codec->extradata_size = 0;
         st->codec->extradata = av_mallocz(atom.size + FF_INPUT_BUFFER_PADDING_SIZE);
         if (!st->codec->extradata)
             return AVERROR(ENOMEM);
@@ -1026,6 +1028,7 @@ static int mov_read_glbl(MOVContext *c, AVIOContext *pb, MOVAtom atom)
             return mov_read_default(c, pb, atom);
     }
     av_free(st->codec->extradata);
+    st->codec->extradata_size = 0;
     st->codec->extradata = av_mallocz(atom.size + FF_INPUT_BUFFER_PADDING_SIZE);
     if (!st->codec->extradata)
         return AVERROR(ENOMEM);
@@ -1051,6 +1054,7 @@ static int mov_read_dvc1(MOVContext *c, AVIOContext *pb, MOVAtom atom)
         return 0;
 
     av_free(st->codec->extradata);
+    st->codec->extradata_size = 0;
     st->codec->extradata = av_mallocz(atom.size - 7 + FF_INPUT_BUFFER_PADDING_SIZE);
     if (!st->codec->extradata)
         return AVERROR(ENOMEM);
@@ -1079,6 +1083,7 @@ static int mov_read_strf(MOVContext *c, AVIOContext *pb, MOVAtom atom)
         return AVERROR_INVALIDDATA;
 
     av_free(st->codec->extradata);
+    st->codec->extradata_size = 0;
     st->codec->extradata = av_mallocz(atom.size - 40 + FF_INPUT_BUFFER_PADDING_SIZE);
     if (!st->codec->extradata)
         return AVERROR(ENOMEM);