diff --git a/stream/stream_concat.c b/stream/stream_concat.c
index 060583a604..21f04f9d62 100644
--- a/stream/stream_concat.c
+++ b/stream/stream_concat.c
@@ -87,6 +87,18 @@ static void s_close(struct stream *s)
         free_stream(p->streams[n]);
 }
 
+// Return the "worst" origin value of the two. cur can be 0 to mean unset.
+static int combine_origin(int cur, int new)
+{
+    if (cur == STREAM_ORIGIN_UNSAFE || new == STREAM_ORIGIN_UNSAFE)
+        return STREAM_ORIGIN_UNSAFE;
+    if (cur == STREAM_ORIGIN_NET || new == STREAM_ORIGIN_NET)
+        return STREAM_ORIGIN_NET;
+    if (cur == STREAM_ORIGIN_FS || new == STREAM_ORIGIN_FS)
+        return STREAM_ORIGIN_FS;
+    return new; // including cur==0
+}
+
 static int open2(struct stream *stream, struct stream_open_args *args)
 {
     struct priv *p = talloc_zero(stream, struct priv);
@@ -104,6 +116,8 @@ static int open2(struct stream *stream, struct stream_open_args *args)
         return STREAM_ERROR;
     }
 
+    stream->stream_origin = 0;
+
     for (int n = 0; n < list->num_streams; n++) {
         struct stream *sub = list->streams[n];
 
@@ -119,6 +133,9 @@ static int open2(struct stream *stream, struct stream_open_args *args)
         if (!sub->seekable)
             stream->seekable = false;
 
+        stream->stream_origin =
+            combine_origin(stream->stream_origin, sub->stream_origin);
+
         MP_TARRAY_APPEND(p, p->streams, p->num_streams, sub);
     }
 
diff --git a/stream/stream_memory.c b/stream/stream_memory.c
index 01246cf33f..7383ff4d6f 100644
--- a/stream/stream_memory.c
+++ b/stream/stream_memory.c
@@ -79,6 +79,8 @@ const stream_info_t stream_info_memory = {
     .protocols = (const char*const[]){ "memory", "hex", NULL },
 };
 
+// The data is copied.
+// Caller may need to set stream.stream_origin correctly.
 struct stream *stream_memory_open(struct mpv_global *global, void *data, int len)
 {
     assert(len >= 0);