diff --git a/video/fmt-conversion.c b/video/fmt-conversion.c
index 30377735cf..bb296b596d 100644
--- a/video/fmt-conversion.c
+++ b/video/fmt-conversion.c
@@ -67,7 +67,8 @@ static const struct {
     {IMGFMT_NV12,  AV_PIX_FMT_NV12},
     {IMGFMT_NV21,  AV_PIX_FMT_NV21},
     {IMGFMT_Y8,    AV_PIX_FMT_GRAY8},
-    {IMGFMT_YA8,   AV_PIX_FMT_GRAY8A},
+    // FFmpeg prefers AV_PIX_FMT_GRAY8A, but Libav has only Y400A
+    {IMGFMT_YA8,   AV_PIX_FMT_Y400A},
     {IMGFMT_Y16_LE, AV_PIX_FMT_GRAY16LE},
     {IMGFMT_Y16_BE, AV_PIX_FMT_GRAY16BE},
     {IMGFMT_410P,  AV_PIX_FMT_YUV410P},