diff --git a/libavcodec/pgssubdec.c b/libavcodec/pgssubdec.c
index 8b088bda8f..55eda4c2a9 100644
--- a/libavcodec/pgssubdec.c
+++ b/libavcodec/pgssubdec.c
@@ -713,4 +713,5 @@ const AVCodec ff_pgssub_decoder = {
     .close          = close_decoder,
     .decode         = decode,
     .priv_class     = &pgsdec_class,
+    .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE,
 };