diff --git a/libavcodec/libvpxenc.c b/libavcodec/libvpxenc.c
index f5506f7e61..5f3c32a598 100644
--- a/libavcodec/libvpxenc.c
+++ b/libavcodec/libvpxenc.c
@@ -667,6 +667,9 @@ static int vp8_encode(AVCodecContext *avctx, AVPacket *pkt,
             v_plane = av_malloc(frame->linesize[2] * frame->height);
             memset(v_plane, 0x80, frame->linesize[2] * frame->height);
             rawimg_alpha->planes[VPX_PLANE_V] = v_plane;
+            rawimg_alpha->stride[VPX_PLANE_Y] = frame->linesize[0];
+            rawimg_alpha->stride[VPX_PLANE_U] = frame->linesize[1];
+            rawimg_alpha->stride[VPX_PLANE_V] = frame->linesize[2];
         }
         timestamp                   = frame->pts;
         if (frame->pict_type == AV_PICTURE_TYPE_I)