diff --git a/libavcodec/pnmdec.c b/libavcodec/pnmdec.c
index bb2ce53496..f012ed288b 100644
--- a/libavcodec/pnmdec.c
+++ b/libavcodec/pnmdec.c
@@ -513,5 +513,6 @@ const FFCodec ff_phm_decoder = {
     .priv_data_size = sizeof(PNMContext),
     .init           = phm_dec_init,
     FF_CODEC_DECODE_CB(pnm_decode_frame),
+    .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE,
 };
 #endif