diff --git a/libavcodec/snow.c b/libavcodec/snow.c
index a3e6afc86a..584be1578c 100644
--- a/libavcodec/snow.c
+++ b/libavcodec/snow.c
@@ -491,7 +491,7 @@ av_cold int ff_snow_common_init(AVCodecContext *avctx){
     FF_ALLOCZ_ARRAY_OR_GOTO(avctx, s->spatial_dwt_buffer,  width, height * sizeof(DWTELEM),  fail); //FIXME this does not belong here
     FF_ALLOCZ_ARRAY_OR_GOTO(avctx, s->temp_dwt_buffer,     width, sizeof(DWTELEM),  fail);
     FF_ALLOCZ_ARRAY_OR_GOTO(avctx, s->temp_idwt_buffer,    width, sizeof(IDWTELEM), fail);
-    FF_ALLOC_ARRAY_OR_GOTO(avctx,  s->run_buffer,          ((width + 1) >> 1), ((height + 1) >> 1) * sizeof(*s->run_buffer), fail);
+    FF_ALLOC_ARRAY_OR_GOTO(avctx,  s->run_buffer,          ((width + 1) >> 1) * ((height + 1) >> 1) + 1, sizeof(*s->run_buffer), fail);
 
     for(i=0; i<MAX_REF_FRAMES; i++) {
         for(j=0; j<MAX_REF_FRAMES; j++)