diff --git a/demux/demux.c b/demux/demux.c
index 88c4374e63..8d30a5ddac 100644
--- a/demux/demux.c
+++ b/demux/demux.c
@@ -2227,9 +2227,9 @@ static bool read_packet(struct demux_internal *in)
     bool eof = true;
     if (demux->desc->read_packet && !demux_cancel_test(demux))
         eof = !demux->desc->read_packet(demux, &pkt);
-    update_cache(in);
 
     pthread_mutex_lock(&in->lock);
+    update_cache(in);
 
     if (pkt) {
         assert(pkt->stream >= 0 && pkt->stream < in->num_streams);
@@ -2508,9 +2508,7 @@ static bool thread_work(struct demux_internal *in)
             return true; // read_packet unlocked, so recheck conditions
     }
     if (mp_time_us() >= in->next_cache_update) {
-        pthread_mutex_unlock(&in->lock);
         update_cache(in);
-        pthread_mutex_lock(&in->lock);
         return true;
     }
     return false;
@@ -3075,11 +3073,11 @@ void demux_update(demuxer_t *demuxer, double pts)
     assert(demuxer == demuxer->in->d_user);
     struct demux_internal *in = demuxer->in;
 
+    pthread_mutex_lock(&in->lock);
+
     if (!in->threading)
         update_cache(in);
 
-    pthread_mutex_lock(&in->lock);
-
     pts = MP_ADD_PTS(pts, -in->ts_offset);
 
     struct timed_metadata *prev = lookup_timed_metadata(in, in->last_playback_pts);
@@ -4021,15 +4019,17 @@ static void update_bytes_read(struct demux_internal *in)
     in->byte_level_seeks += new_seeks;
 }
 
-// must be called not locked
+// must be called locked, temporarily unlocks
 static void update_cache(struct demux_internal *in)
 {
     struct demuxer *demuxer = in->d_thread;
     struct stream *stream = demuxer->stream;
 
-    // Don't lock while querying the stream.
     struct mp_tags *stream_metadata = NULL;
 
+    // Don't lock while querying the stream.
+    pthread_mutex_unlock(&in->lock);
+
     int64_t stream_size = -1;
     if (stream) {
         stream_size = stream_get_size(stream);
@@ -4059,8 +4059,6 @@ static void update_cache(struct demux_internal *in)
     // The idea is to update as long as there is "activity".
     if (in->bytes_per_second)
         in->next_cache_update = now + MP_SECOND_US + 1;
-
-    pthread_mutex_unlock(&in->lock);
 }
 
 static void dumper_close(struct demux_internal *in)