diff --git a/fftools/ffmpeg.h b/fftools/ffmpeg.h
index cc72b1cb6e..25c33cf207 100644
--- a/fftools/ffmpeg.h
+++ b/fftools/ffmpeg.h
@@ -659,7 +659,6 @@ typedef struct OutputStream {
 
     const char *attachment_filename;
     int copy_initial_nonkeyframes;
-    int copy_prior_start;
 
     int keep_pix_fmt;
 
diff --git a/fftools/ffmpeg_mux.c b/fftools/ffmpeg_mux.c
index 01ccac55ce..f52205cf30 100644
--- a/fftools/ffmpeg_mux.c
+++ b/fftools/ffmpeg_mux.c
@@ -398,7 +398,7 @@ void of_streamcopy(OutputStream *ost, const AVPacket *pkt, int64_t dts)
         return;
 
     if (!ms->streamcopy_started) {
-        if (!ost->copy_prior_start &&
+        if (!ms->copy_prior_start &&
             (pkt->pts == AV_NOPTS_VALUE ?
              dts < ms->ts_copy_start :
              pkt->pts < av_rescale_q(ms->ts_copy_start, AV_TIME_BASE_Q, pkt->time_base)))
diff --git a/fftools/ffmpeg_mux.h b/fftools/ffmpeg_mux.h
index 0938a261ee..81c4698161 100644
--- a/fftools/ffmpeg_mux.h
+++ b/fftools/ffmpeg_mux.h
@@ -75,6 +75,7 @@ typedef struct MuxStream {
     // combined size of all the packets sent to the muxer
     uint64_t data_size_mux;
 
+    int copy_prior_start;
     int streamcopy_started;
 } MuxStream;
 
diff --git a/fftools/ffmpeg_mux_init.c b/fftools/ffmpeg_mux_init.c
index 555ccfd796..51fdd88232 100644
--- a/fftools/ffmpeg_mux_init.c
+++ b/fftools/ffmpeg_mux_init.c
@@ -908,7 +908,7 @@ static int streamcopy_init(const Muxer *mux, const OptionsContext *o,
     if (ost->st->duration <= 0 && ist->st->duration > 0)
         ost->st->duration = av_rescale_q(ist->st->duration, ist->st->time_base, ost->st->time_base);
 
-    if (!ost->copy_prior_start) {
+    if (!ms->copy_prior_start) {
         ms->ts_copy_start = (mux->of.start_time == AV_NOPTS_VALUE) ?
                             0 : mux->of.start_time;
         if (copy_ts && ifile->start_time != AV_NOPTS_VALUE) {
@@ -1156,8 +1156,8 @@ static OutputStream *ost_add(Muxer *mux, const OptionsContext *o,
         }
     }
 
-    ost->copy_prior_start = -1;
-    MATCH_PER_STREAM_OPT(copy_prior_start, i, ost->copy_prior_start, oc ,st);
+    ms->copy_prior_start = -1;
+    MATCH_PER_STREAM_OPT(copy_prior_start, i, ms->copy_prior_start, oc ,st);
 
     MATCH_PER_STREAM_OPT(bitstream_filters, str, bsfs, oc, st);
     if (bsfs && *bsfs) {