diff --git a/libavcodec/mmvideo.c b/libavcodec/mmvideo.c
index 11a819dc6d..8dfcc71934 100644
--- a/libavcodec/mmvideo.c
+++ b/libavcodec/mmvideo.c
@@ -248,4 +248,5 @@ const AVCodec ff_mmvideo_decoder = {
     .close          = mm_decode_end,
     .decode         = mm_decode_frame,
     .capabilities   = AV_CODEC_CAP_DR1,
+    .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE,
 };