diff --git a/libavcodec/ffv1enc.c b/libavcodec/ffv1enc.c
index 97b38e4d16..8e5ebe773c 100644
--- a/libavcodec/ffv1enc.c
+++ b/libavcodec/ffv1enc.c
@@ -1684,9 +1684,11 @@ size_t ff_ffv1_encode_buffer_size(AVCodecContext *avctx)
 {
     FFV1Context *f = avctx->priv_data;
 
-    size_t maxsize = avctx->width*avctx->height * (1 + f->transparency);
+    int w = avctx->width  + f->num_h_slices;
+    int h = avctx->height + f->num_v_slices;
+    size_t maxsize = w*h * (1 + f->transparency);
     if (f->chroma_planes)
-        maxsize += AV_CEIL_RSHIFT(avctx->width, f->chroma_h_shift) * AV_CEIL_RSHIFT(f->height, f->chroma_v_shift) * 2;
+        maxsize += AV_CEIL_RSHIFT(w, f->chroma_h_shift) * AV_CEIL_RSHIFT(h, f->chroma_v_shift) * 2;
     maxsize += f->slice_count * 800; //for slice header
     if (f->version > 3) {
         maxsize *= f->bits_per_raw_sample + 1;