diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index 96f51547c0..70f0aa8ef8 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -3472,6 +3472,11 @@ static int mov_write_ftyp_tag(AVIOContext *pb, AVFormatContext *s)
             ffio_wfourcc(pb, "avc1");
     }
 
+    // We add tfdt atoms when fragmenting, signal this with the iso6 compatible
+    // brand. This is compatible with users that don't understand tfdt.
+    if (mov->flags & FF_MOV_FLAG_FRAGMENT)
+        ffio_wfourcc(pb, "iso6");
+
     if (mov->mode == MODE_3GP)
         ffio_wfourcc(pb, has_h264 ? "3gp6":"3gp4");
     else if (mov->mode & MODE_3G2)
diff --git a/tests/ref/fate/sub-movtextenc b/tests/ref/fate/sub-movtextenc
index e79df0f6c5..09d92beb34 100644
--- a/tests/ref/fate/sub-movtextenc
+++ b/tests/ref/fate/sub-movtextenc
@@ -1 +1 @@
-f632afed498634a01b9c5ae5a2228012
+d26e73c420c40a00225060d2e6532df9
diff --git a/tests/ref/lavf/ismv b/tests/ref/lavf/ismv
index c54b857ca6..c87cf6e471 100644
--- a/tests/ref/lavf/ismv
+++ b/tests/ref/lavf/ismv
@@ -1,9 +1,9 @@
-564eaa3553ce02cf0921cd647fa4e6d2 *./tests/data/lavf/lavf.ismv
-312606 ./tests/data/lavf/lavf.ismv
+56193aebd2845871f4e91956b3e4dea5 *./tests/data/lavf/lavf.ismv
+312610 ./tests/data/lavf/lavf.ismv
 ./tests/data/lavf/lavf.ismv CRC=0xb7d29d29
-53f0506abc827a6540a9faf5e3b761c0 *./tests/data/lavf/lavf.ismv
-321512 ./tests/data/lavf/lavf.ismv
+19c7e128c52d7a1d7a1921d60774a785 *./tests/data/lavf/lavf.ismv
+321516 ./tests/data/lavf/lavf.ismv
 ./tests/data/lavf/lavf.ismv CRC=0x33834815
-564eaa3553ce02cf0921cd647fa4e6d2 *./tests/data/lavf/lavf.ismv
-312606 ./tests/data/lavf/lavf.ismv
+56193aebd2845871f4e91956b3e4dea5 *./tests/data/lavf/lavf.ismv
+312610 ./tests/data/lavf/lavf.ismv
 ./tests/data/lavf/lavf.ismv CRC=0xb7d29d29