diff --git a/libavfilter/vf_thumbnail.c b/libavfilter/vf_thumbnail.c
index 8cda7b45f1..728880e100 100644
--- a/libavfilter/vf_thumbnail.c
+++ b/libavfilter/vf_thumbnail.c
@@ -189,7 +189,7 @@ static void get_hist16(int *hist, const uint8_t *p, ptrdiff_t stride,
         }
         /* handle tail */
         for (int x = width4; x < width; x++)
-            hist[p16[x]]++;
+            hist[(uint8_t) (p16[x] >> shift)]++;
         p += stride;
     }