diff --git a/libavcodec/mss4.c b/libavcodec/mss4.c
index c421a07c5d..a6d036f3f7 100644
--- a/libavcodec/mss4.c
+++ b/libavcodec/mss4.c
@@ -678,5 +678,5 @@ AVCodec ff_mts2_decoder = {
     .close          = mss4_decode_end,
     .decode         = mss4_decode_frame,
     .capabilities   = AV_CODEC_CAP_DR1,
-    .caps_internal  = FF_CODEC_CAP_INIT_CLEANUP,
+    .caps_internal  = FF_CODEC_CAP_INIT_CLEANUP | FF_CODEC_CAP_INIT_THREADSAFE,
 };