diff --git a/libavfilter/vf_fieldmatch.c b/libavfilter/vf_fieldmatch.c
index 5a73eb43b8..8d1e68b85f 100644
--- a/libavfilter/vf_fieldmatch.c
+++ b/libavfilter/vf_fieldmatch.c
@@ -938,7 +938,7 @@ static int config_input(AVFilterLink *inlink)
     fm->tpitchy  = FFALIGN(w,      16);
     fm->tpitchuv = FFALIGN(w >> 1, 16);
 
-    fm->tbuffer = av_malloc(h/2 * fm->tpitchy);
+    fm->tbuffer = av_calloc((h/2 + 4) * fm->tpitchy, sizeof(*fm->tbuffer));
     fm->c_array = av_malloc((((w + fm->blockx/2)/fm->blockx)+1) *
                             (((h + fm->blocky/2)/fm->blocky)+1) *
                             4 * sizeof(*fm->c_array));