diff --git a/block/bio.c b/block/bio.c
index c89e402..d512045 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -546,7 +546,7 @@ EXPORT_SYMBOL(zero_fill_bio);
  *   REQ_OP_READ, zero the truncated part. This function should only
  *   be used for handling corner cases, such as bio eod.
  */
-void bio_truncate(struct bio *bio, unsigned new_size)
+static void bio_truncate(struct bio *bio, unsigned new_size)
 {
 	struct bio_vec bv;
 	struct bvec_iter iter;