diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c
index aa05ff020b..03859a9913 100644
--- a/libavcodec/pngdec.c
+++ b/libavcodec/pngdec.c
@@ -489,6 +489,8 @@ static int decode_frame(AVCodecContext *avctx,
                     avctx->pix_fmt = PIX_FMT_MONOBLACK;
                 } else if (s->color_type == PNG_COLOR_TYPE_PALETTE) {
                     avctx->pix_fmt = PIX_FMT_PAL8;
+                } else if (s->color_type == PNG_COLOR_TYPE_GRAY_ALPHA) {
+                    avctx->pix_fmt = PIX_FMT_Y400A;
                 } else {
                     goto fail;
                 }