diff --git a/libavcodec/adxdec.c b/libavcodec/adxdec.c
index bff15d826c..20256a092e 100644
--- a/libavcodec/adxdec.c
+++ b/libavcodec/adxdec.c
@@ -203,4 +203,5 @@ const AVCodec ff_adpcm_adx_decoder = {
                       AV_CODEC_CAP_DR1,
     .sample_fmts    = (const enum AVSampleFormat[]) { AV_SAMPLE_FMT_S16P,
                                                       AV_SAMPLE_FMT_NONE },
+    .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE,
 };