diff --git a/libavcodec/lagarith.c b/libavcodec/lagarith.c
index 35f5a07e4c..e72674c481 100644
--- a/libavcodec/lagarith.c
+++ b/libavcodec/lagarith.c
@@ -553,7 +553,7 @@ static int lag_decode_frame(AVCodecContext *avctx,
 
         if (!l->rgb_planes) {
             l->rgb_stride = FFALIGN(avctx->width, 16);
-            l->rgb_planes = av_malloc(l->rgb_stride * avctx->height * planes);
+            l->rgb_planes = av_malloc(l->rgb_stride * avctx->height * planes + 1);
             if (!l->rgb_planes) {
                 av_log(avctx, AV_LOG_ERROR, "cannot allocate temporary buffer\n");
                 return AVERROR(ENOMEM);