diff --git a/libavcodec/pnm.c b/libavcodec/pnm.c
index 13ecbb057f..e73f5a7acb 100644
--- a/libavcodec/pnm.c
+++ b/libavcodec/pnm.c
@@ -163,6 +163,8 @@ int ff_pnm_decode_header(AVCodecContext *avctx, PNMContext * const s)
         if (s->maxval >= 256) {
             if (avctx->pix_fmt == AV_PIX_FMT_GRAY8) {
                 avctx->pix_fmt = AV_PIX_FMT_GRAY16BE;
+                if (s->maxval != 65535)
+                    avctx->pix_fmt = AV_PIX_FMT_GRAY16;
             } else if (avctx->pix_fmt == AV_PIX_FMT_RGB24) {
                 avctx->pix_fmt = AV_PIX_FMT_RGB48BE;
             } else {