diff --git a/libavcodec/wmavoice.c b/libavcodec/wmavoice.c
index a9d50f95ca..e096b8029d 100644
--- a/libavcodec/wmavoice.c
+++ b/libavcodec/wmavoice.c
@@ -2007,6 +2007,6 @@ const AVCodec ff_wmavoice_decoder = {
     .close            = wmavoice_decode_end,
     .decode           = wmavoice_decode_packet,
     .capabilities     = AV_CODEC_CAP_SUBFRAMES | AV_CODEC_CAP_DR1 | AV_CODEC_CAP_DELAY,
-    .caps_internal    = FF_CODEC_CAP_INIT_CLEANUP,
+    .caps_internal    = FF_CODEC_CAP_INIT_THREADSAFE | FF_CODEC_CAP_INIT_CLEANUP,
     .flush            = wmavoice_flush,
 };