diff --git a/src/utils/bit_writer_utils.c b/src/utils/bit_writer_utils.c
index bd2355a1..1e1f1c72 100644
--- a/src/utils/bit_writer_utils.c
+++ b/src/utils/bit_writer_utils.c
@@ -52,7 +52,7 @@ static int BitWriterResize(VP8BitWriter* const bw, size_t extra_size) {
     WEBP_UNSAFE_MEMCPY(new_buf, bw->buf, bw->pos);
   }
   WebPSafeFree(bw->buf);
-  bw->buf = new_buf;
+  bw->buf = WEBP_UNSAFE_FORGE_BIDI_INDEXABLE(uint8_t*, new_buf, new_size);
   bw->max_pos = new_size;
   return 1;
 }
diff --git a/src/utils/bit_writer_utils.h b/src/utils/bit_writer_utils.h
index d0cdd01d..36704234 100644
--- a/src/utils/bit_writer_utils.h
+++ b/src/utils/bit_writer_utils.h
@@ -32,9 +32,10 @@ typedef struct VP8BitWriter VP8BitWriter;
 struct VP8BitWriter {
   int32_t range;  // range-1
   int32_t value;
-  int run;       // number of outstanding bits
-  int nb_bits;   // number of pending bits
-  uint8_t* buf;  // internal buffer. Re-allocated regularly. Not owned.
+  int run;      // number of outstanding bits
+  int nb_bits;  // number of pending bits
+  // internal buffer. Re-allocated regularly. Not owned.
+  uint8_t* WEBP_SIZED_BY_OR_NULL(max_pos) buf;
   size_t pos;
   size_t max_pos;
   int error;  // true in case of error